KEEP YOUR POOL

BLUE____________

______________________________________________________________

THE CHEMISTRY OF BALANCING WATER

BY

STAN KINGSLEY

A Self-Published eBOOK

A Manual for Home Owners

written and published by

Stan Kingsley

A Digital Electronic Book

Available to All Without Charge as a PDF File

COPYRIGHTS AND PERMISSIONS

Copyright © 2012 by the author. All rights reserved.

For permission to reproduce or distribute for commercial gain or to publish in

some other format please contact the author by email at:

Stan817Kingsley@att.net

For questions and comments and if you would like to compensate the author

(via PayPal) please use the same address.

Version 20120817 (August 17, 2012)

Non-fiction: How To, Swimming Pool Water Maintenance, Chlorination

Foreword

Because this book is a digital electronic file (pdf) viewable on your computer the

contents can be searched using the search function and sidebar. These functions vary

depending on which version of software you have. An outline of the contents follows.

Use key words or the title words to get to that section. A search labeled KEY POINTS

should list the pages summarizing each main topic.

The meat of the book is in the middle -- Achieving Balanced Water and

Maintaining Balanced Water. The earlier sections describe the basic chemistry and

definitions. Later sections have details about pool chemicals.

I first wrote this manual more than twenty-five years ago for myself. There was

not much written about pool care back then. Suppliers had started to provide written

information but, not unexpectedly, they had a slant which promoted their products, not

all of which were useful. Since that time computer aided analysis became widely

available in pool stores. I've updated the contents to reflect these changes as well as

new products. The most useful products and test procedures have remained the same

for a long time and are only aided by computers, not replaced by them.

There are many ways to purify pool water but I have selected only one,

chlorination, and have provided recommendations that balance economics with

convenience to make maintaining pool water less of a chore and less of an expense.

There are tens of thousands of technical pages written about water and its analysis

and water treatments. Even though the chemistry might seem complicated I have only

included enough to explain why certain effects happen in pool water. For further

information any topic today can be searched on the internet for more details.

In twenty-five years I have used only liquid and tablet chlorine along with acid

and baking soda (and occasionally calcium chloride because I live in a soft water

area). Nothing else is needed. Once a pool is balanced it is much easier and cheaper

to maintain it than it is to neglect it and fix it later. But even then a large dose of liquid

chlorine is usually all that is required plus balancing the calcium and pH. My pool has

always been blue.

It is also eco-friendly to maintain pool water in the most efficient ways possible.

The methods described in this manual should help you save time and money and help

the environment too. It is good to be "green" while keeping your pool water blue.

I am a retired scientist with degrees in chemistry and business administration. I

hope that what I have learned about pool water maintenance will be useful to you also.

The most practical points are collected in "key points" and I will start with a summary of

those.

/// *KEY POINTS* SUMMARY \\\

1.) If you are using chlorine to sanitize a swimming pool keep the pH near 7.4.

2.) There are two forms of economical chlorine -- solution (10%) and tablets (3" diameter).

3.) If stabilizer is present the chlorine will last longer but must be kept at a higher level. Too much stabilizer will throw off test results and interfere with chlorination.

4.) To preserve the cement the water must be balanced and the pH buffered. Hydrochloric acid and baking soda are the two chemicals needed for this.

5.) Calcium is required at about 300 ppm to preserve the cement and make water balance easier to maintain. Hard water requires adjusting other parameters.

6.) The best algaecide is liquid chlorine. Others are almost never required.

7.) Balanced water is blue, clear and odor-free.

8.) pH is the single most important test. It indicates the activity level of the chlorine.

9.) The only chemicals you need to use the methods described in this manual are chlorine tablets and solution, baking soda and acid. And calcium in soft water areas.

10.) Two necessary pieces of equipment are a pool thermometer and a comprehensive test kit which includes a nomogram for water balance.

Note: There is a short QUIZ at the very end. You may want to try it first.

Note: The "pool chemical data sheets" can be listed by typing the word data in thesearch window. They are good summaries of the chemicals and their use.

OUTLINE

INTRODUCTIONWhy Chlorine?It's All About Water BalanceIf In Doubt

CHLORINATION

CHLORINE SOLUTIONChemistry of Liquid ChlorineHandling of Liquid ChlorineKEY POINTS ABOUT CHLORINE SOLUTION

CHLORINE TABLETSChemistry of Trichlor TabletsHandling of Trichlor TabletsKEY POINTS ABOUT TRICHLOR TABLETS

CHLORINE POWDERChemistry of Calcium HypochloriteHandling of Calcium HypochloriteKEY POINTS ABOUT CALCIUM HYPOCHLORITE

STABILIZERProblems Caused By High Stabilizer ConcentrationKEY POINTS ABOUT STABILIZER

CONTROL OF pHDissociation of WaterDefinition of pHScale Of pH ValuesBufferingCorrecting Low pHWhy pH Increases And Alkalinity DecreasesCarbonate ChemistryKEY POINTS ABOUT pH CONTROL

CALCIUM BALANCECalcium Chloride: Chemistry and HandlingCalcium ConcentrationProblems with Hard WaterCalcium Balance and TemperatureCalcium Carbonate (Cement) SolubilityA Short Cut To Balance WaterUsing A NomogramSaturation IndexKEY POINTS ABOUT CALCIUM BALANCE

IDEAL CONDITIONS

WEATHER EFFECTSSeasonal Effects -- SummerSeasonal Effects -- WinterThe Effect Of RainEvaporationIncoming Water SupplyEnvironmentKEY POINTS ABOUT WEATHER EFFECTS

CONTROL OF ALGAESuper-chlorinationShock TreatmentOther Chlorine TreatmentsOther AlgaecidesQuaternary Ammonium ChloridesCost ComparisonKEY POINTS ABOUT CONTROL OF ALGAE

TESTING AND ADJUSTING POOL WATER

TEST KITSAccuracy of Test ResultsChlorine Test Methods: OTO vs. DPD

pH DETERMINATIONAcid DemandBase Demand

CHLORINE CONCENTRATIONChlorine MeasurementsEstimating Effective Chlorine (VERY IMPORTANT)Adjusting Chlorine

TOTAL ALKALINITY

CALCIUM HARDNESS

STABILIZER CONCENTRATION

TESTING CONDUCTIVITY

KEY POINTS ABOUT TESTING

SAMPLING THE WATER

RECORD KEEPING

CALCULATIONSParts Per MillionAmount of Chemical Additions

PARTIAL DRAINING OF THE POOL

OLD SCHOOL VS. NEW SCHOOL

POOL WATER PROBLEMSAlgaeAlgae With High ChlorineCloudy, Hazy WaterColored WaterFoamingOdorsHigh Dissolved SolidsHigh Filter PressureRough Deposits On Pool SurfacesCement Erosion

HOW TO AVOID BIG PROBLEMS

ACHIEVING BALANCED POOL WATER

MAINTAINING BALANCED POOL WATERSummer ProceduresOff-Season ProceduresOff-Season Time Saver

QUARTERLY TESTING TO MAINTAIN A BALANCED POOL

SEASONAL CHECK LIST

CHEMICAL SUPPLIES

KEY POINTS ABOUT MAINTAINING POOL WATER

EQUIPMENT CHECK LIST

FILTERINGCartridge FiltersDE FiltersPump Schedule

BRUSHING AND VACUUMING SKIMMER

PUMP TRAP

SAFETYRisks of Swimming In Chlorinated Water

COST ANALYSISPurchasing Chemical SuppliesCosts of TestingActual Annual Costs

POOL CHEMICAL DATA SHEETS

SUMMARY OF POOL CHEMICALS AND RECOMMENDED USES

QUIZ

/// INTRODUCTION \\\

This manual is for the home owner with a cement in-ground swimming pool. It

is a brief description of the necessary chemicals and procedures for using chlorine to

sanitize pool water. An attempt has been made to take the mystery out of the

chemistry.

Why Chlorine?

Chlorination has been used for over a century in public water supplies and

pools because it is safe and effective and low cost compared to the many other

methods which are not discussed here, such as bromination, ozonation, peroxides

and silver ions.

The three most widely used and readily available chlorine compounds are:

* Chlorine solution (sodium hypochlorite in water, very similar to bleach)

* Trichlor tablets (trichloro-s-triazinetrione powder in 3" tablet form)

* Calcium hypochlorite powder (granules similar to bleach)

What they are and how to use them is discussed in detail with suggestions for

making them the most effective at least cost to maintain your pool water. Comparisons

to other forms of chlorine are given.

It's All About Water Balance

Chlorination to kill bacteria and algae is the first step. The second aspect of

pool maintenance is water balance. It is necessary to control the pH by buffering the

water to keep it near neutral, slightly basic, so that it is never acidic and corrosive. The

third step is calcium balance to preserve the cement as long as possible.

If In Doubt

The suitability of the information in this manual and its application to particular

situations has to be determined by the reader. Always read the labels of the chemicals

before using and follow the instructions for safe handling and use. Consult a

professional when in doubt.

Now on to the technical stuff! There are explanations for the technical terms

and a simplified description of the chemistry. It may not seem simple to the average

pool owner without training in chemistry but the emphasis is on the basic mechanisms

at work in pool water treatment and why they affect decisions about which products to

use and how to use them. Each section is followed by KEY POINTS which are useful

for quick reference when it comes time to practice the art of water maintenance. They

are a summary of important points and recommendations. Without knowing the basics

it is easy to be led into wasting money on expensive materials when cheaper ones will

do or into chasing a problem around and around by attacking appearances rather than

true causes.

/// CHLORINATION \\\

The chemical species which sanitizes is hypochlorous acid, HOCl. It is the

active form of chlorine.

Chlorine compounds used in pools form hypochlorous acid when added to

water. The amount formed depends on the pH. In very acidic water all of the chlorine

will be in the active form. In basic water it remains inactive as hypochlorite ions. In

normal pool water the chlorine is a mixture of both active and inactive forms.

If this chemical terminology seems obscure it is only necessary to remember

that THE EFFECTIVENESS OF THE CHLORINE DEPENDS ON THE pH OF THE

WATER.

CHLORINE SPECIES IN WATER

Hypochlorous acid HOCl Active species, effective purifying agent

Hypochlorite ion OCl– Inactive species, becomes active at lower pH

Chloride ion Cl– Inactive species, forms salt

When testing for chlorine the test kit methods will indicate the sum of both the

active and inactive forms. The results can only be interpreted along with the pH value.

As described later the pH of pool water must be maintained in a narrow range for

several reasons. The amount of active chlorine will be anywhere from one-fourth to

three-fourths of the total when the pH is in the proper range. It increases when the pH

is lowered, that is, when acid is added.

TO OBTAIN A SUFFICIENT LEVEL OF ACTIVE CHLORINE IN POOL WATER IT

IS NECESSARY TO ADD A CHLORINE CONTAINING COMPOUND AND MAINTAIN

THE pH NEAR 7.4.

The three best materials for effective chlorination at low cost are described in

the next three sections. Each ends with a summary of KEY POINTS about that

material.

What Is The Right Amount of Chlorine?

It is often recommended that one part per million is sufficient. This is

approximately the amount of chlorine in most tap water. It might be OK for a short time

but it is so marginal that you would be constantly adjusting it upward. Pool books and

test kits often recommend three to five parts per million. This is a good range and

matches the range for most test methods for pool chlorine. When stabilizer is present

more chlorine is needed so I find that four to five or more parts per million is a more

practical chlorine level to aim for in swimming pools. This too can vary with the water

temperature, number of pool users and the weather. Public pools usually aim for ten

parts per million because they have so many users.

How Do You Know When You Have Enough Chlorine?

If algae shows up you need more chlorine. An immediate boost will kill the

algae and then a higher level in general will help prevent it from coming back. An

appropriate level of chlorine will prevent the appearance of algae on an on-going

basis. And, again, this depends on climate, weather and pool use. It is better to spend

a little more on regular chlorination and keep the level near four or five ppm rather

than have to shock the pool with ten or more parts per million.

/// CHLORINE SOLUTION (Sodium hypochlorite) \\\

Liquid chlorine is a ten percent solution of sodium hypochlorite (NaOCl) in

water. It is available in pre-packaged one gallon containers or in bulk at hardware or

pool supply stores. The bulk material is usually sold in two and a half gallon refillable

containers.

Chemistry of Liquid Chlorine

When liquid chlorine is added to a pool it immediately raises the level of

effective chlorine. Sodium hypochlorite is instantly converted to HOCl depending on

the pH, that is, the availability of acid ions (H+) in the water.

As acid ions are taken up to form the hypochlorous acid the pH of the pool

increases. This is one of the disadvantages of liquid chlorine because the pH must be

brought back to the desired range by the addition of acid to the pool water. Adding

hydrochloric acid lowers the pH and adds chloride ions (Cl–) which do not contribute

to effective chlorination.

Handling of Chlorine Solution

Liquid chlorine must be handled carefully. A splash can ruin your clothes. A

spill in your car would be a disaster. It is the same active ingredient as household

bleach but at double the concentration. Use caution when transporting or pouring

liquid chlorine.

HELPFUL HINTS: Use a box to keep the container from touching the car

interior. Carry the container without bumping it against yourself and only put it down

on something that will not be ruined by stray drips of the solution. Never mix the

solution with anything else. Only pour it into a clean measuring container. Avoid

breathing the vapors.

The ten percent concentration is only approximate. The storage life is limited so

the percentage will drop over time. Do not buy more than a season's supply at a time.

In spite of the inconveniences it is the most commonly used form of chlorine because it

is cheap and effective.

The change in chlorine level with the addition of chlorinating solution is

immediate. However, the level drops substantially within one or two days. This rate of

disappearance of chlorine is typical and depends on sunlight, temperature and the

presence of stabilizer and contaminants in the pool water.

Ten percent chlorine solution is added at about 500 ml (one pint) per day every

day to achieve a one part per million (ppm) chlorine level in a 15,000 gallon pool.

/// *KEY POINTS* ABOUT CHLORINE SOLUTION \\\

1.) The chlorine level is raised immediately as the solution is added.

2.) The chlorine protection only lasts a short time.

3.) The pool's pH rises when chlorine solution is added so it must be re-adjusted

with acid.

4.) Handle it carefully -- it is a hazardous material.

5.) It is the most cost effective form of chlorine.

6.) Use it for routine chlorination, superchlorination and shock treatments.

7.) The shelf life is limited.

/// CHLORINE TABLETS (Trichlor) \\\

The recommended stabilized chlorine is the three-inch tablet form of trichloro-s-

triazinetrione ("trichlor"). It is available under several brand names and all

manufacturer's labels include the following:

trichloro-s-triazinetrione 99.0%inert 1.0%available chlorine (89%)

Do not use stabilized chlorine with less available chlorine, such as "dichlor". Do

not confuse stabilized chlorine with tablets of calcium hypochlorite.

Comparing prices tablets are more expensive than liquid chlorine. This cost

difference is partially offset because trichlor tablets provide stabilizer. Also the trichlor

compound does not affect the pH and so reduces the requirements for acid.

Chemistry of Trichlor Tablets

Trichloro-s-triazinetrione is an organic compound which contains three chlorine

atoms per molecule. When these chlorine atoms are released they combine with

hydroxyl groups present in the water and form hypochlorous acid (HOCl). At the same

time three acid groups present in the water combine with the remainder of the trichlor

to form one cyanuric acid (CYA) molecule. Cyanuric acid is a stabilizer for chlorine. It

is discussed in the section on STABILIZER.

Chlorinating tablets are like time-release capsules. Chlorination is provided

over a long period of time at a slow rate. As the tablet dissolves the chlorine level

increases slowly and reaches a peak several days later. Most of the chlorine will be

released in the first two weeks. Three-inch tablets are preferred because it takes

about three weeks for them to completely dissolve.

Handling of Trichlor Tablets

They are easier to handle and transport than liquids. But if uncovered they give

off obnoxious fumes. It is best to wear rubber gloves when transferring tablets from

their original container to a pool dispenser. Or plastic tongs can be used to avoid skin

contact with the tablet.

Because they dissolve slowly the three inch tablets eliminate the need for daily

attention. The best way to control the rate of chlorination is to use a floating dispenser

which can be loaded once a week.

Three-inch tablets are added two tablets per week to achieve about one ppm

chlorine in a 15,000 gallon pool.

/// *KEY POINTS* ABOUT TRICHLOR TABLETS \\\

1.) When trichlor tablets dissolve they slowly create hypochlorous acid (the effective form of chlorine).

2.) Stabilizer (cyanuric acid) is also released but at one-third the rate of the hypochlorous acid.

3.) Continuous use of trichlor tablets causes the amount of cyanuric acid stabilizer to increase.

4.) Limit use to avoid excess stabilizer.

5.) Use tablets during the hottest time of the year for routine chlorination.

/// CHLORINE POWDER (Calcium hypochlorite) \\\

A third type of chlorine which is useful in pools is calcium hypochlorite. Its

physical form is solid, usually a powder. It can also be found as tablets, but do not

confuse it with trichlor tablets. Look for the following description on the label:

calcium hypochlorite 65%inert ingredients 35%available chlorine (65%)

The cost of calcium hypochlorite varies with quantity and packaging, from 100

pound drums to 25 pound pails or one pound packages.

Chemistry of Calcium Hypochlorite

When calcium hypochlorite is added to a pool it raises the level of effective

chlorine as it dissolves and it raises the pH. Its chemistry is similar to liquid chlorine

but with calcium in place of sodium. The addition of calcium to the pool water is an

advantage in most cases unless the water is hard meaning that there is already a high

level of calcium in it. See the section CALCIUM BALANCE for problems with hard

water.

Handling of Calcium Hypochlorite

Calcium hypochlorite is easier to transport than liquid chlorine and easier to

handle than trichlor. The shelf life is substantially longer than that of chlorine solution.

A disadvantage of calcium hypochlorite is that it causes cloudy pool water until the

filter removes residual particles.

The level of chlorine is raised quickly as the powder dissolves. The denser

forms (tablets or cartridges) will be slower to dissolve and are added less often. They

behave like time release capsules.

The powdered form of calcium hypochlorite can offer an advantage when used

as a shock treatment to kill algae. The powder can be sprinkled on or near algae

spots. When this is done in still water the concentration of chlorine becomes very high

right where the algae is. Some powders are finer and dissolve faster providing a

quicker shock and some are 75% active.

One pound of 65% active powder provides a 5 ppm chlorine shock in a 15,000

gallon pool.

About three ounces per day of calcium hypochlorite powder in a 15,000 gallon

pool will provide about one ppm chlorine.

/// *KEY POINTS* ABOUT CALCIUM HYPOCHLORITE \\\

1.) The powder form of calcium hypochlorite quickly raises the effective chlorine concentration.

2.) The tablet or cartridge form of calcium hypochlorite slowly releases effective chlorine.

3.) It causes the pH to go up.

4.) It provides calcium, necessary for pool water, but a problem in hard water areas or when calcium content is already high.

5.) The powder form is an excellent algaecide, especially for spots or clusters of algae.

COMPARISON OF CHLORINE COMPOUNDS

Name: Sodium Calcium Trichloro-s-hypochlorite hypochlorite triazinetrione

Formula: NaOCl Ca(OCl)2 (CNOCl)3

Form: Solution Powder Tablet (3")

% Active: 10% active 65 to 75% active 99% active

Provides: HOCl HOCl, calcium HOCl, stabilizer

Chlorination: Excellent Good Excellent

Use rate: 16 oz daily 3 oz daily 16 oz weekly

Shock: Excellent Good Not recommended

Spot algaecide: Not recommended Excellent Not recommended

/// STABILIZER (Cyanuric acid) \\\

Chlorine compounds decompose when exposed to sunlight (ultra-violet

radiation). This happens to hypochlorous acid in pool water. Cyanuric acid (CYA)

stabilizes hypochlorous acid and extends its lifetime. Stabilizer concentration should

be kept under 100 ppm. About 30 ppm is optimum. A good starting range is 20 to 40

ppm. Higher amounts are required in summer along with higher chlorine

concentrations. Indoor pools do not require stabilizer.

When trichlor tablets are used stabilizer is formed as they dissolve. If trichlor is

not used cyanuric acid stabilizer can be added separately. For example, adding five

pounds would provide 40 ppm in a 15,000 gallon pool. (See the sections on

CALCULATIONS and ADDITIONS TO THE POOL.) Cyanuric acid is sometimes called

conditioner but it acts as a stabilizer.

When trichlor tablets are added routinely to the pool the amount of cyanuric acid

(CYA) will increase by about 3 ppm per month. This effect is very important. Because

the cyanuric acid (CYA) level can become excessive if using trichlor continuously at

least twice a year determine its concentration. If it is too high then one of the other

non-stabilized forms of chlorine should be used instead of trichlor until the level of

CYA comes down below 50 ppm. Be aware that other forms of chlorine may be

stabilized and their use will increase the CYA levels in your pool.

Problems Caused By High Stabilizer Concentration

If the CYA level becomes too high it will interfere with the activity of the chlorine.

The test kit results can show adequate levels of chlorine but there may still be algae

growth. If the pool is super-chlorinated the level of chlorine will remain very for a very

long time during which it should not be used.

Cyanuric acid (CYA) is very useful but only at a reasonable level. Any amount

over 100 ppm is too much. It is better to never exceed 60 ppm. If the level of CYA is

very high there is only one way to reduce it: Drain about half the pool and refill to cut

the concentration in half. Caution: See the section: Partial draining of the Pool. In

less severe cases simply stop using the trichlor type of chlorine -- the stabilizer

concentration will drop by about 7 ppm per month.

High cyanuric acid (CYA) levels also interfere with the test for alkalinity. At less

than 30 ppm the effect on the alkalinity test is small enough to be ignored. But in large

amounts CYA can mask a low level of bicarbonate alkalinity. See the section TOTAL

ALKALINITY in TESTING AND ADJUSTING POOL WATER.

For these reasons it is recommended that trichlor be used for only four months

of the year to avoid excessive build-up of stabilizer, cyanuric acid.

/// *KEY POINTS* ABOUT STABILIZER \\\

1.) At about 30 ppm it extends the lifetime of chlorine.

2.) Too much stabilizer inhibits the effectiveness of chlorine.

3.) Stabilizer contributes to alkalinity in the test for total alkalinity.

4.) Too much of it will mask a deficiency in carbonate level unless the alkalinity test result is corrected for it.

5.) The amount of cyanuric acid in the pool water increases when stabilized chlorine is used continuously for long periods of time.

6.) When the stabilizer level is high do not use trichlor (or any stabilized chlorine product); use sodium or calcium hypochlorite instead.

/// CONTROL OF pH \\\

Dissociation of Water

Water is unstable and to a very small degree its molecules dissociate. They

break down into ion pairs -- one hydrogen ion (H+) and one hydroxyl ion (OH-). The

balance between (H+) ions and (OH-) ions is easily influenced by other molecules. If

the balance favors the (H+) ions the water is acidic. When the amounts of (H+) ions

and (OH-) ions are equal then the water is neutral. If the (OH-) ions predominate then

the water is basic. A chemist would describe the dissociation as follows:

H2O = (H+) + (OH–)

water forms hydrogen ions and hydroxyl ions

(acidic) (basic)

Definition of pH

The balance between the dissociated ions is referred to as "pH." It is measured

on a scale which runs from zero to fourteen. (It happens to be the negative logarithm

of the concentration of hydrogen ions (H+) expressed in moles per liter.) Because of

the way it is defined neutral water has a pH of 7. Acidic water is less than seven, down

to zero. Basic water has a pH over 7 up to 14. The pH value is the strength of the

hydrogen ion concentration. It is an abbreviation of the German phrase "potenz

Hydrogen," literally "power of hydrogen."

Scale Of pH Values

neutral

0----------------------------------7---------------------------------14

acidic basic

For swimming pool water the desired range of pH is within 7 to 8, always on the

slightly basic side. Acidic pool water would be corrosive. Above pH 8 there would be

very little of the active form of chlorine. Recall that hypochlorous acid becomes

inactive hypochlorite ion in strongly basic water.

For these reasons the ideal value of pH is around 7.4 (with an acceptable range

of 7.2 to 7.6) where the water is not corrosive and about one half of the chlorine will be

in the active form.

Buffering

Buffering is a method of slowing down changes in pH. Materials are added to

the water which will counteract increases or decreases in the pH. In swimming pools

this is accomplished by adding baking soda (sodium bicarbonate).

The amount of baking soda required is about one hundred ppm, primarily to

prevent cement corrosion (see CALCIUM BALANCE) but also to provide buffering

action for pH stability. The level of sodium bicarbonate will change relatively slowly

and can be adjusted about every two weeks. It is checked with a test for total alkalinity.

The pH has to be adjusted more often. In buffered swimming pools the normal

drift will be to higher pH. Also, as described earlier the use of sodium or calcium

hypochlorite will raise the pH. These changes are corrected by the addition of acid.

Most commonly muriatic (hydrochloric) acid is used. It is more cost effective than dry

acid (sodium bisulfate). The pH adjustment with acid should always be the last thing

done when treating pool water. (See below.)

Correcting Low pH

Acid additions should always be done such that the pH never goes below 7.

However, if the pH should accidentally go below 7 it can be corrected in several ways:

*A slightly acidic pool just under pH 7 can be corrected by adding liquid or powder chlorine (sodium or calcium hypochlorite).

*A pool with mildly acidic water (pH about 6) can be corrected by adding baking soda.

*Sodium carbonate (Na2CO3) can be used to adjust a very low pH pool. This material is sold under various names for raising pool pH. It should never be needed but if the occasion arises a pool store would be able to provide it. There is no need to keep it on hand.

Why pH Increases And Alkalinity Decreases

Acids and bases (alkaline materials) neutralize each other and form salts. In

pool water the acid and bicarbonate combine to form carbonic acid. Carbonic acid

decomposes to water and carbon dioxide gas. When this happens the carbonate and

acid ions are lost. All that remains is sodium and chloride, salt. The decrease in

carbonate reduces the alkalinity. The decrease in acid raises the pH. The

accumulation of salt raises the total dissolved solids.

All of these changes are unavoidable and this is why the baking soda and acid

must be replenished. All of this happens faster when the temperature is higher. To

minimize the neutralization of baking soda by the acid it is best to adjust alkalinity first

and then adjust the pH. Doing this in the other order can result in a never-ending

consumption of both materials as they are converted into salt.

Carbonate Chemistry

The chemical formula for sodium bicarbonate is NaHCO3.

In water it provides bicarbonate ions (CO3–), carbonate ions (CO3– –) or

carbonic acid (H2CO3) depending on the pH.

Each carbonate ion can take up two acid ions and bicarbonate can take one.

This is why sodium carbonate will more effectively raise pH.

The pH of carbonate is 11 and the pH of bicarbonate is 8.5 in unbuffered water.

At pH three both of them are completely converted to carbonic acid.

At normal pool pH values the buffering system is actually a bicarbonate/

carbonic acid mixture. This happens because the pool pH lies between the pH's of

these two species. It doesn't matter whether bicarbonate (baking soda) or carbonate

(soda ash) is added to the pool water. Once the pH is adjusted to the normal range of

7.2 to 7.6 the same species are formed. This is the reason that there is no need for

carbonate addition and the less expensive baking soda is used.

/// *KEY POINTS* ABOUT pH CONTROL \\\

1.) Because it determines the effectiveness of chlorine pH is the most important item to control to maintain pool water.

2.) A pH of 7.4 is the best value (as a high in summer and as a low in winter).

3.) The usual range is 7.2 to 7.6 for pH.

4.) Almost always the pH will drift higher.

5.) Hydrochloric (muriatic) acid is used to adjust the pH back to lower values.

6.) Adjusting pH should always be done after making all other additions to the pool water.

7.) Maintenance of pH is often a daily task (in season).

8.) Baking soda is used to retard changes in pH.

9.) Determining the baking soda content (the total alkalinity test) should be done about every two weeks.

10.) The correct amount of baking soda (bicarbonate alkalinity) is about 90 ppm. (It will vary with temperature and calcium content. See the section on CALCIUM BALANCE.)

/// CALCIUM BALANCE \\\

In-ground swimming pools are usually made by casting concrete over a metal

frame of reinforcing rods. The interior surface of the pool is finished with a coating of

cement containing marble dust ("plaster") to give it a bright white color. Concrete,

cement and marble are principally or entirely limestone which is the mineral name for

calcium carbonate.

The pool surface in contact with water is going to slightly dissolve and put

calcium and carbonate in the water. To prevent the cement surfaces from eroding

calcium and carbonate should be added to the pool water.

Carbonate is supplied when baking soda (sodium bicarbonate) is added. See

the section on CONTROL OF pH. Calcium is provided by the addition of calcium

chloride.

Calcium Chloride: Chemistry and Handling

Calcium chloride is a chemical similar to ordinary salt. It absorbs moisture so it

is usually available in its hydrate form, calcium chloride dihydrate (at 80%, mixed with

other chlorides). Higher purity pellets are also available.

The chemical formula is CaCl2.2(H2O).

It can be purchased as a brand name product or in bulk form. Hardware supply

stores offer large bags of bulk calcium chloride at lower prices per pound. Smaller

quantities or brand name products will cost more.

The best way to add calcium is to fill a clean five gallon pail with pool water and

add a few pounds of calcium chloride. When it dissolves it gives off heat. The solid

material or its hot concentrated solution can be irritating to skin. Carefully pour the

calcium solution into the skimmer leaving any solid materials in the bottom of the pail.

Repeat this procedure until the required amount of calcium has been dissolved and

added. Or flakes of calcium chloride can be added slowly to the skimmer so that they

dissolve before reaching the pump.

Calcium Concentration

A calcium concentration near 300 ppm is best. A suitable range is 200 to 400

ppm. When the calcium level is controlled fairly closely it is easier to maintain the

proper chemical balances. Testing every three months will usually be sufficient. A

new pool or one recently resurfaced may change more quickly than an older pool and

not need additional calcium for a long time.

It is important to remember that the routine use of calcium hypochlorite will add

significantly to the calcium level of the pool water. See the section on CHLORINE

POWDER. Its use as an algaecide or for shock treatments will not contribute much to

the calcium level -- about 2 ppm per treatment. However, routine chlorination with this

material will add about 20 ppm per month. This is not a problem for most pools and

simply reduces the requirement for adding calcium chloride. For pools with an existing

high level of calcium, calcium hypochlorite must be avoided.

Problems with Hard Water

High calcium levels can be the result of naturally occurring levels in the

incoming water used to fill the pool. Some water supplies are naturally "hard" and can

contain so much calcium that scaling becomes a problem. This happens when

calcium carbonate precipitates out of the pool water as a hard rough deposit on the

walls of the pool. Often high calcium content can be compensated by altering

carbonate concentration and pH. In areas where the problem is severe it may be

necessary to bring in water with a lower calcium content from another location.

The presence of calcium (and similar ions such as magnesium) is said to make

water "hard" because it interferes with the sudsing action of detergents. In some test

kits the calcium determination is referred to as a "water hardness" or "calcium

hardness" test.

Calcium Balance and Temperature

Temperature changes the solubility of chemicals in water. In particular the

solubility of calcium carbonate will change. As its temperature changes it is possible

for pool water to become corrosive and dissolve the cement. Or it is possible that

calcium carbonate will begin to precipitate. This can cause cloudiness in the water,

scale formation on equipment or rough deposits on the walls of the pool.

This problem was addressed by chemists who developed a saturation index for

calcium carbonate. It is a way of calculating the amount of calcium and carbonate

needed for a given pH and temperature to prevent corrosion (dissolving cement) and

scaling (precipitating calcium carbonate).

Calcium Carbonate (Cement) Solubility

Most minerals are more soluble in warm water than cold. Calcium carbonate is

unusual in this respect -- it becomes less soluble as the temperature increases. This is

why a lower carbonate (lower alkalinity) level is necessary in hotter weather. And the

acidity should be higher (lower pH) in warmer water because of the decreased

solubility of the calcium carbonate.

One approach for counterbalancing the solubility of the cement requires

changing the pH to compensate for temperature changes. The calcium and carbonate

concentrations are kept constant. A set of conditions satisfying these requirements is

given below:

BALANCED WATER CONDITIONS

Water temperature (ºF) 85º 60º

Calcium (ppm) 300 300

Alkalinity, total (ppm) 90 90

pH 7.3 7.5

Note that the alkalinity is the same and the calcium concentration is the same.

The change in water temperature is compensated by altering the pH. Over a wide and

useful range of temperature the water can be balanced with the calcium concentration

near 300 ppm. The total alkalinity shown above includes 80 ppm for carbonate

alkalinity and 10 ppm for the effect of stabilizer.

This shows that it is particularly helpful to keep the calcium level near 300 ppm.

With this level of calcium the pH can be kept in the range where the chlorine is

effective.

Another way to look at the problem of balancing the water is given below.

A Short Cut To Balance Water

Calcium balance is complicated because there are four items to be concerned

about. With two of these kept in a narrow range -- calcium around 300 ppm and the

pH around 7.4 -- the problem is simplified. Now it is only necessary to alter the

carbonate alkalinity to suit the temperature.

In the range of 60 to 90ºF the alkalinity can be adjusted as shown below:

BALANCED WATER CONDITIONS AT pH 7.4

Temperature (ºF) Total Alkalinity (ppm)

90 75

80 85

70 100

60 115

For most pools this is a good approach because alkalinity can be easily

changed in response to seasonal temperatures. Since calcium levels are slow to

change it is easier to maintain them at a uniform level. The pH is restricted to a narrow

range because of its effect on chlorine.

For a heated pool kept at constant temperature the problem of calcium balance

is much simpler. A carbonate level can be selected for the given temperature and a

pH of 7.4. It is still necessary to test and adjust the pH, calcium and carbonate to

maintain the selected levels.

For pool water which is hard it is necessary to use a calcium to carbonate ratio

outside the normal range. And sometimes the temperature falls outside the range

covered in the table above. In these cases a nomogram will make it easier to find the

right amount of alkalinity to use.

Using A Nomogram

The word nomogram is a combination of Greek words meaning a law which is

written or drawn, in this case a scientific law which describes the solubility of calcium

and carbonate as determined by the temperature and pH.

A good test kit will include a nomogram which is a way to compare these four

items. The nomogram could be a series of tables or more conveniently it will be a

device like a slide rule. A test kit which includes a nomogram for water balance is well

worth the cost.

The nomogram will cover a wide range of conditions but only those which keep

the pH between 7 and 7.6 are of interest. It is best to start with the water temperature

and set it against a pH of 7.4 Next find the alkalinity which compensates the existing

calcium level. If the calcium level is less than 220 ppm consider adjusting it to 300

ppm and find the amount of alkalinity to balance it. Once the alkalinity has been

selected it can be maintained until there is a large temperature change.

The nomogram is especially useful if your water supply is hard and has a

calcium level higher than 400 ppm. In this situation locate the value of the calcium

level and find an alkalinity value which will balance the water at a useful pH for the

given temperature. Since it is not easy to lower calcium it will be necessary to adjust

alkalinity to lower levels to compensate for it. In this way the necessary pH can be

maintained for effective chlorination over the seasonal temperature range of the pool.

Saturation Index

The saturation index, also called the Langlier index, is a measure of the water

balance. It is the difference in the pH of your pool water compared to the pH at which

calcium is saturated at the temperature and alkalinity of your pool water. Most

computer analyses of pool water will include a value for the saturation index. It is the

single most comprehensive indicator of how well your water is balanced. When the

difference between your pool's pH and the pH of saturation for calcium is zero your

pool water is perfectly balanced.

An acceptable range for the saturation index is plus or minus 0.3 pH units.

When your pool's pH is greater by 0.3 pH units that condition can lead to scaling, the

precipitation of calcium as hard lumps on the pool surfaces. When your pool's pH is

less by 0.3 pH units that condition is corrosive. So at a saturation index over +0.3 you

need to add acid to lower the pH. When the saturation index is under --0.3 you need

to add baking soda. The computer's computation of the saturation index is only as

good as an accurate measure of pH, temperature, alkalinity and hardness.

/// *KEY POINTS* ABOUT CALCIUM BALANCE \\\

1.) Calcium is necessary to preserve the cement finish of the pool surfaces.

2.) The desired range for calcium is 200 to 400 ppm.

3.) Calcium hardness should be determined at least four times a year. A new or

recently resurfaced pool should be checked more often.

4.) The amount of calcium and the amount of carbonate necessary to preserve the

cement depend on the pH and the water temperature.

5.) If the pH is kept near 7.4 and the calcium concentration is near 300 ppm then

the alkalinity can be adjusted to compensate for seasonal changes in the water

temperature.

6.) The desired amount of alkalinity can be determined from a set of tables (or a

nomogram) which compares levels of calcium and carbonate with pH and

temperature.

7.) My personal preference is to keep the calcium concentration on the high side

at about 500 ppm so that the alkalinity and pH can be kept lower during the

summer.

/// IDEAL CONDITIONS \\\

There are two materials which are necessary for water maintenance using the

method described in this manual: CHLORINE -- to disinfect the water, and CALCIUM

-- to preserve the cement.

Chlorine effectiveness depends on pH and stabilizer. Calcium solubility

depends on pH and carbonate alkalinity.

The ideal values for these items and the acceptable ranges are given below:

Ideal Range

Chlorine (effective) 2 ppm 1 - 3 ppm

Stabilizer 25 ppm 10 - 40 ppm

pH (to activate the Cl) 7.4 7.2 - 7.6

Calcium 300 ppm 200 - 400 ppm

Carbonate alkalinity 80 ppm 60 - 120 ppm

Total alkalinity (test kit) 90 ppm 70 - 130 ppm

Total alkalinity is shown separately from carbonate alkalinity because it is the

one actually measured and it differs because of the influence of the stabilizer.

The "ideal" water temperature for ideal conditions is 77ºF. Since water

temperature can vary or be set to a different value there has to be a range of

acceptable values for the other parameters.

In warmer water the chlorine and stabilizer requirements are higher. The pH

should be slightly lower (more acidic). The carbonate alkalinity should be lower. The

calcium can be maintained near 300 ppm.

In cooler water the chlorine and stabilizer requirements are lower and

maintaining lower levels will reduce costs. The pH can be kept slightly higher (less

acidic) which also reduces the cost. The carbonate alkalinity should be higher. The

calcium can be maintained near 300 ppm.

Although calcium balance allows for some variations in the concentrations of

calcium and carbonate a minimum carbonate alkalinity of 60 ppm and maximum

calcium level of 600 should be observed.

Remember that ideally the saturation index (Langlier index) will be zero with an

acceptable range of plus or minus 0.3 pH units. That measure is a combination of the

temperature, pH, calcium hardness and carbonate alkalinity. A computer can provide

the calculation for it.

/// WEATHER EFFECTS \\\

Even in a stable climate (such as Florida) pool water can change from below

60ºF in winter to above 90ºF in summer. It is important to have a pool thermometer. As

shown above in IDEAL CONDITIONS calcium balance, buffering and chlorination all

depend on water temperature.

Seasonal Effects -- Summer

When the water is 20ºF warmer changes occur twice as fast -- algae and

bacteria breed faster, stabilizer decomposes faster, bicarbonate and acid neutralize

faster -- and there is more use of the pool in hotter weather. The most direct ultra-violet

radiation occurs at the summer solstice (June 22 in the northern hemisphere). These

conditions cause changes in the requirements to maintain balanced water.

The chlorine and stabilizer levels have to be kept higher to avoid depletion

because the consumption of chlorine is greater. The pH can be adjusted to lower

values (7.2 to 7.4) to make the chlorine more effective. The alkalinity can be kept at

the lower end of its range (60 to 80 ppm). This will be more compatible with a lower

pH and reduce acid demand. These changes will make the precipitation of calcium

carbonate less likely during very hot weather.

Seasonal Effects -- Winter

When water temperatures drop (especially below 60ºF) there is much less

demand on the chlorine. If the pool is kept open chlorine can be kept lower at one

ppm and the pH kept at 7.4 to 7.5. Higher alkalinity is required (120 ppm). Stabilizer

concentration should be lower, near the winter solstice, December 22. Cold weather

is an opportunity to reduce costs because less chemical treatment is needed.

The Effect Of Rain

Rain upsets balanced water. It carries dust, dirt, organic matter, pollen, algae

and bacteria into the pool. This causes more of the chlorine to be used and the pH to

rise. The cure for this is simple -- add liquid or power chlorine, then adjust the pH.

The pH of rain is near 5 or 6. It is acidic because it combines with carbon

dioxide in the air and forms carbonic acid. Buffered pool water overcomes this pH

difference; in fact the pool pH becomes less acidic because of the materials carried

along with the rain.

For a typical pool a half inch of rain will be about one percent of the volume;

dilution is not great unless there is a downpour. Heavy rain will require draining some

water and adjusting chlorine, alkalinity and pH (in this order). If possible it is best to

have the pool water circulating during rain.

Evaporation

In windy, dry, hot conditions an outdoor pool exposed to the sun could lose

several inches of water in a week. Normal evaporation is less than this and with luck

rain will balance losses. When luck does not prevail it will be necessary to add water

to the pool.

Incoming Water Supply

Residential water supplies can vary depending on the geographic location.

Test the water supply with a pool test kit. This is especially useful when filling a pool.

It is important to remember that municipal water supplies are treated and have

alkalinity and calcium levels that can be substantial. Most municipal water

departments will share their test results.

A typical comparison of tap water, pool water and rain is shown in the table

below:

WATER SUPPLY COMPARISONS

Tap Water Pool Water Rain

Chlorine, free (ppm) 1 2 0

pH 9.5 7.4 5

Alkalinity, total (ppm) 60 95 0

Calcium (ppm) 80 300 0

Stabilizer (ppm) 0 25 0

Environment

Proximity of trees, plants and uncovered soil will affect the amount of dust,

leaves, pine needles, pollen and organic matter blown into the pool. A screen pool

enclosure will greatly reduce the amount of contamination. Careful selection and

placement of decorative plants and the use of mulch or stone near the pool perimeter

can also reduce cleaning chores.

/// *KEY POINTS* ABOUT WEATHER EFFECTS \\\

1.) Rain upsets balanced water requiring additional chlorine and acid.

2.) Hot summer weather increases the need for chlorine; alkalinity and pH should be kept at the lower end of their acceptable ranges.

3.) Cold winter weather is an opportunity to save chemical supplies since demands on chlorine are lower and the pH can be higher.

4.) With more intense sunlight (near the summer solstice) more chlorine and stabilizer are required.

/// CONTROL OF ALGAE \\\

The most common pool problem is algae growth. Even a brief lapse in

maintaining the chlorine level or the pH can result in algae blooms, especially after a

rainy or windy day.

One of the most effective algaecides is chlorine. It is also the cheapest and

should be the first choice among the methods to combat algae growth.

Super-chlorination

Bringing the chlorine concentration to a higher than normal level is called

"superchlorination." Because it immediately raises chlorine levels the use of liquid

chlorine provides the best effect. When the first bloom of algae growth is noticed

doubling the normal chlorine level will often kill it. This treatment should be

accompanied by brushing the pool surfaces. The filter will remove the dead algae.

The pool should not be used until the chlorine level returns to the normal range.

Occasional superchlorination will also remove combined chlorine which builds

up when waste material is disinfected. It is convenient to do this when the pool will not

be in use for a day or two. Ideal times to super-chlorinate are when rain is expected or

if going on a short trip and leaving the pool unused.

Shock Treatment

If there is a lot of algae or if it resists superchlorination then a larger dose of

chlorine can be used. This is called "shocking " the pool. Again liquid chlorine is an

excellent way to increase chlorine levels immediately to a high value. The amount of

chlorine to use depends on the severity of the problem. Most often 30 to 60 ppm will

take care of a major algae bloom. This is ten to twenty times the usual amount so it

will take a while for the chlorine to return to normal. Do not use the pool until the

excess chlorine has dissipated.

To make superchlorination or shock more effective the chlorine compound can

be added at the end of the day when the water is not circulating. First adjust the pH to

7.2 before turning off the pump. Then add the chlorine to the water along the

perimeter of the pool. During the night the chlorine level will be highest near the walls

where most algae usually forms. The next morning the pH can be checked after

circulating the pool water for half an hour and adjusted as necessary. Note that

superchlorination will usually boost chlorine for about two days whereas shock

treatment will take several days longer.

In pools which are seldom used or used by one person the need for shock

treatment is rare. In pools which are used by many people, especially in hot weather,

superchlorination and shock will be needed more frequently. Shocking the pool water

is usually required only if the maintenance has been neglected. In a well maintained

pool it would never be required. But if the pool water turns dark green it is definitely

time to shock treat the water. If a pool is going to be left unattended for a period of time

preventive shock treatment can be used to avoid algae growth.

Many times when a pool has a strong odor it is not the chlorine that causes it but

rather the by-product of chlorine and urine which is chloramines. This should

definitely be treated by superchlorination or shock.

Other Chlorine Treatments

In addition to sodium hypochlorite solution there are three powders which are

also very effective algaecides:

(1) Calcium hypochlorite. See the section CHLORINE POWDER. This

material is an excellent choice for control of algae spots. It can be applied directly in

the vicinity of the algae when the pool is not circulating to raise the chlorine level very

high in a localized area.

It is also very good for superchlorination and shock. Since it is chemically

similar to liquid chlorine it will require pH adjustment in the same manner.

(2) Trichloro-s-triazinetrione (trichlor) powder. This is the same material as

discussed in the section CHLORINE TABLETS. Powered trichlor is sold specifically as

a treatment for "black algae." It could harm the cement surface.

(3) Lithium hypochlorite. It is an excellent material but very expensive. It

could be used if both calcium and stabilizer levels were too high preventing the use of

either of the other two powders.

NOTE: Using spot algaecides should be avoided since strong solid chlorine

compounds can dissolve cement surfaces weakening them and making them rougher

which then promotes algae growth. The first attempt to kill algae should use liquid

chlorine then powders can be used with the water circulating. Spots of algae can also

be brushed with a stainless steel brush to help break them open.

Other Algaecides

Before buying a high priced algaecide it is a good idea to check the label. If it is

just an expensive form of chlorine it will not be any more effective than the cheaper

forms. There are some very exotic algaecides available and they have higher costs.

Before resorting to these materials it is better to try shocking the pool with liquid

chlorine. Then try powdered chlorine compounds applied in the area of the algae

colony. If these attempts do not kill the algae consult a pool store about the problem

for a recommendation about one of the more specialized types.

Quaternary Ammonium Chlorides

There is a family of common algaecides known as quaternary ammonium

chlorides (also called "alkyl ammonium chlorides"). They are available from several

manufacturers as ten percent solutions in one gallon containers. At higher cost this

material provides an alternate way to defend against algae and bacteria which is

chemically different from chlorination. A small addition each week of a quaternary

ammonium chloride solution is an optional preventive measure. The use of this

material imparts a slippery feel to the water which may be unwanted. With larger

amounts foaming will occur. They are not recommended.

Cost Comparison

The relative costs of these algaecide and shock treatments are listed below.

The prices are in dollars per pound of active ingredient (which is not the same as the

shelf price in the store). The prices of almost all of these items have gone up since this

list was prepared but the comparisons are still valid. Currently liquid chlorine prices in

Florida have doubled as I type this but the list still shows the expected relative

expense of each type of chlorine.

Sodium hypochlorite solution, bulk (2.5 gallon jug) 1.00

" " one gallon, prepackaged 1.70

Calcium hypochlorite (powder) 3.00

Quaternary ammonium chlorides (solution) 5.00

Trichloro-s-triazinetrione (trichlor), powder 7.50

Lithium hypochlorite (powder) 20.00

It is easy to see that sodium hypochlorite should be the first choice for shocking

or super-chlorinating. The calcium hypochlorite at slightly higher cost is a useful

alternative.

Fighting algae is always a situation where an ounce of prevention is worth a

pound of cure. And a dollar's worth of chlorine is better than a more expensive

algaecide.

/// *KEY POINTS* ABOUT CONTROL OF ALGAE \\\

1.) The most cost effective algaecide is chlorine solution, ten percent sodium

hypochlorite: One gallon provides 5 ppm chlorine in 15,000 gallon pools.

2.) For algae on the bottom of a pool a chlorine powder is more effective, added

when the water is still. The most cost effective powder is calcium hypochlorite:

One pound provides 5 ppm chlorine in 15,000 gallon pools.

3.) Expensive algaecides are not more effective and usually not required.

Note: My personal preference for treating algae or stains on the bottom of a pool is

to use chlorine solution instead of a powder. The liquid chlorine can be

applied by pouring it through a tube such as the brush pole, with the brush

and handle removed. This requires some dexterity, and a funnel helps, but

it puts liquid chlorine at high concentration right at the place where it is needed.

Obviously, the pool water should not be circulating while doing this.

Note: Algae is air-borne. It is always present. You can control it so that it is not

visible, but it is never completely absent from a pool.

/// TESTING AND ADJUSTING POOL WATER \\\

TEST KITS

A test kit is the most important piece of equipment needed for maintaining pool

water. There are many available. It is very advantageous to purchase a kit that

includes all five of the necessary tests:

pH determinationchlorine concentrationtotal alkalinitycalcium hardnessstabilizer concentration (cyanuric acid)

Accuracy of Test Results

If in doubt about the accuracy of a test repeat it with new reagents. The cost of a

second test is small compared to the trouble that comes with inaccurate test results. If

the actual pH is higher than indicated the chlorine is less effective. Or, if the pH is

actually lower the water could be corrosive to the cement. The test kit and its reagents

should be stored indoors out of direct sunlight. It does not have to be refrigerated.

Chlorine Test Methods: OTO vs. DPD

There are two methods for measuring chlorine commonly available in pool test

kits. They are referred to as "OTO" and "DPD" which are abbreviations for the reagents

used in the test. The DPD method offers the advantage of using two separate steps to

find the free and total chlorine levels. The OTO test indicates free chlorine for a few

seconds after which total chlorine is indicated. They both provide satisfactory results

but the DPD method is easier to interpret.

pH DETERMINATION

The pH determination indicates the basicity of the pool water. Refer to the

section on CONTROL OF pH. Test kits are designed so that the appropriate pH level

will be approximately in the middle of the test kit range. In a normal buffered pool the

pH will drift to higher values and it will be necessary to bring it back down by adding

acid.

Acid Demand

The amount of acid required is often referred to as "acid demand." For example,

the amount of acid required to change the pH from 7.8 to 7.3 in a 15,000 gallon pool

with 100 ppm of carbonate alkalinity is 325 ml (ten ounces) of concentrated

hydrochloric acid (muriatic acid). This amount can be calculated based on the

chemical interactions of the bicarbonate buffer and the acid.

Fortunately it is not necessary to calculate acid demand each time the pH

changes. Large test kits include a test for this and a table for determining how much

acid should be added. Drops of a standard acid solution ("acid demand reagent") are

added to the pH sample until the desired pH is reached. The number of drops

represents the amount of acid needed for the pool size as listed in the table.

Once familiar with the procedure the amount of acid for a desired change in pH

is easily estimated. Usually 100 to 300 ml (three to ten ounces) of acid will lower the

pH as required. It can be added directly to the pool water or diluted first. But is should

always be added slowly. Rapid addition of acid will reduce the alkalinity more and

change the pH less effectively.

Base Demand

There is a similar test and table for "base demand." This is rarely needed. In a

carefully maintained pool the water will never become too acidic. However, if there is

an accidental upset of the pH to values below 7 the base demand test may be useful.

See the section "Correcting Low pH."

CHLORINE CONCENTRATION

A good test kit will provide two tests for chlorine determination. One for "free

chlorine" and one for "total chlorine." The difference between them is the "combined

chlorine" level. Combined chlorine is produced when chlorine combines with waste

material to disinfect it. Chemically it is usually a chloramine. In a residential pool there

may be some combined chlorine if it has had heavy use but most of the time there will

be little or none. Periodic super-chlorination removes the combined chlorine.

The most important chlorine level cannot be directly tested. It is the effective

chlorine which is pH dependent. Unless both the free chlorine and the pH are in

range there is very little purifying or sanitizing.

Chlorine Measurements

Total chlorine is a measure of all the chlorine materials present in the pool

water. This includes hypochlorous acid, hypochlorite ion and chloramines. It does not

include chlorides (from salt or acid). It can be determined by the DPD or OTO method.

Free chlorine is a measure of hypochlorous acid and hypochlorite ion. It is

easiest to determine with the DPD method.

Combined chlorine is found by subtracting the free chlorine from the total

chlorine. It should be close to zero.

Effective chlorine is hypochlorous acid. It is pH dependent and is usually about

half of the free chlorine level.

CHLORINE TESTS AND MEASUREMENTS (Summary)

TOTAL chlorine (test) HOCl, OCl–, chloramines

FREE chlorine (test) HOCl, OCl–

COMBINED chlorine (calculated) chloramines (TOTAL – FREE)

EFFECTIVE chlorine HOCl (depends on pH)

Estimating Effective Chlorine (VERY IMPORTANT)

To estimate effective chlorine first measure the free chlorine with a DPD test.

Next reduce this amount by half to allow for the pH effect. If stabilizer is present (and

below 40 ppm) subtract another ten percent. If stabilizer is over 100 ppm effective

chlorine will be substantially reduced.

For example, if the free chlorine test reads 3 ppm then the effective level is 1.5

ppm (with the pH near 7.4). With CYA stabilizer at 30 ppm the effective chlorine is

further reduced to about 1.35 ppm.

In a second case if free chlorine were again 3 ppm but the pH was 7.6 with 100

ppm of stabilizer then the effective chlorine would be less than 0.5 ppm. In the first

example algae growth would be inhibited but not in the second, especially in hot

weather, even though the test results are the same.

Adjusting Chlorine

Liquid chlorine (sodium hypochlorite) can be added directly to the pool. Pour it

slowly along the perimeter for even distribution. Do not pour chlorine solution into the

skimmer -- it could corrode the filter.

Chlorine powder (calcium hypochlorite) can be added directly to the water

along the perimeter of the pool or cast over the surface. An alternate method

recommended by some manufacturers is to pre-dissolve the powder in a bucket and

pour the solution in the pool. Again, do not put this type of chlorine into the skimmer

(either the solid or a solution of it ) because it could corrode the filter.

Never toss tablets in the pool; they will corrode the cement. There are three

ways to handle them:

1.) They can be placed in the skimmer basket which causes them to dissolve faster.

This is only recommended if there are no metal parts in the pool plumbing.

2.) They can be added to a floating dispenser which allows them to dissolve slowly

and provides better distribution even when the pump is not running.

3.) There are in-line dispensers which can be connected to the piping of the water

circulation system. The tablets are added to a small tank and dissolve as pool

water is pumped through it. However, controlling the rate of addition is more

reliable with the floating device.

Hypochlorites (either solution or powder) last for a period of days whereas

tablets last for a period of weeks. With more frequent but smaller additions of either

type of chlorine the minimum amount remains at a higher, more effective level. This is

more cost effective but less convenient than using larger amounts less often.

It would be ideal to add small amounts continuously. In practice only the

chlorine and acid additions are critical since only the pH and chlorine concentration

can change rapidly. With hypochlorites (liquid or powder) more frequent correction of

pH is required -- daily additions of chlorine and acid will often be needed to maintain a

steady level of effective chlorine. With trichlor tablets (three-inch size) used in a

floating dispenser weekly addition is enough.

TOTAL ALKALINITY

Any material which takes up acid ions will contribute to total alkalinity.

Sometimes "total alkalinity" is referred to as "carbonate" alkalinity because it is the

bicarbonate concentration which is important. Since the pH determines the state of the

carbonate ion it will affect the test results; so pH has to be close to normal to get an

accurate result. (See the section on Carbonate Chemistry.)

The total alkalinity test should be performed at least every two weeks (once a

week in hot weather). When an addition of baking soda is needed it can be added

slowly into the skimmer. With the water circulating it will dissolve quickly.

The stabilizer compound (CYA) interferes with this test because it contributes to

alkalinity. About one third of it shows up. Typically this will add about ten ppm.

However, if the stabilizer is excessive (over 100 ppm) then it will contribute more than

30 ppm. It would be necessary to adjust for such a large interference since it is only

the bicarbonate which balances the water. When testing alkalinity remember to

reduce the "total" to estimate the bicarbonate content if stabilizer is present.

CALCIUM HARDNESS

The test for calcium is actually a water hardness test which also responds to

other minerals such as magnesium. This is not a problem for most pools since calcium

will predominate. However, in a hard water area the amount of the other minerals

present must be known in order to adjust for the interference. Public water utilities

should provide this information. A private well would have to be tested for minerals

other than calcium.

Calcium hardness should be tested every three months. Normally calcium will

drift to lower values and can be corrected with the addition of calcium chloride. If the

calcium level should go up unexpectedly the cement may be dissolving. Unless the

supply water is hard or a lot of calcium hypochlorite has been used there is a problem

with the water balance (alkalinity and pH). See the section on CALCIUM BALANCE.

STABILIZER CONCENTRATION

The test for cyanuric acid (CYA) is very important if a stabilized chlorine

compound is used. Continuous use of trichloro-s-triazinetrione (trichlor) causes the

level of stabilizer to increase. After three months the stabilizer content should be

determined. It is best to stay under 50 ppm. This is necessary to keep excessively

high levels from interfering with the chlorine activity or the determination of alkalinity.

This test is imprecise because it requires estimating the cloudiness (turbidity) of

the test solution. The easiest way to avoid excess is to limit the amount of stabilized

chlorine used for a season. There is no need for this test if neither stabilized chlorine

nor cyanuric acid is used, or if the amounts are limited.

TESTING CONDUCTIVITY

The conductivity of the pool water indicates the amount of dissolved solids in

the water, most of which is salt. The buffering and pH adjustments using bicarbonate

and acid cause salt to form. As the salt increases the conductivity increases.

This test can be done at a pool store; it is not critical. Once a year ask for a

determination of "total dissolved solids." Compare it with the tap water at the pool site.

When too high reduce it by draining some of the water and adding fresh water. (There

are some pools which use salt in the water for purification with automatic chlorinators.

In this case the conductivity should be higher than normal.)

TESTING SCHEDULES -- FREQUENCY

pH determination Almost daily

Chlorine concentration Several times a week

Total alkalinity Twice a month

Calcium hardness Four times a year

Stabilizer concentration Two to four times a year

Conductivity Once a year

/// *KEY POINTS* ABOUT TESTING \\\

1.) The amount of effective chlorine is the test kit measurement adjusted for pH and

the presence of stabilizer. It is lower than the test reading, usually by half.

2.) Accurate pH testing is essential to water maintenance based on chlorination.

3.) A complete test kit with a nomogram is the best choice to do your own

testing. It will put YOU in control of your pool.

/// SAMPLING THE WATER \\\

For meaningful results the water sample must represent the average condition

in the pool. For this reason the water should be circulating at least half an hour before

the sample is taken. Always use clean sampling containers and rinse them out after

each test. Do not discard the tested water into the pool.

If test results from samples taken at different locations are compared usually no

differences are found. Try this in your pool. If the results are different is may mean that

the circulation is not very effective. Check the outlets for the incoming water. Most can

be adjusted to change the direction of the water flow.

/// RECORD KEEPING \\\

A calendar is a convenient way to save test results. On a monthly calendar

each day's test results or chemical additions can be recorded in the appropriate space.

A notebook is useful for recording test results that are done less frequently such

as calcium and stabilizer levels. All the tests should be done together at least four

times a year. A record of these results is useful in developing an understanding of the

effects of the chemical additions.

/// CALCULATIONS \\\

Parts Per Million

Except for pH all other tests determine concentrations in "parts per million." It is

abbreviated as "ppm." It refers to the weight of the tested chemical compared to the

weight of the water in the pool.

The weight of water is 8.3 pounds per gallon. For a 15,000 gallon pool the

weight of the water is 8.3 times 15,000 which equals 124,500 pounds. Dividing this

weight by one million gives 0.1245 pounds. Therefore "one ppm" in a 15,000 gallon

pool is 0.1245 pounds which is about two ounces or 56 grams. If a 15,000 gallon pool

needed 20 ppm of a chemical then 20 times 0.1245 would be 2.5 pounds, the required

amount to add.

The chemical compounds are usually not 100% of the desired material so this

must also be taken into account. For example the different chlorine compounds are

different percentages of available chlorine.

It is not necessary to do these calculations each time an addition to the pool

water is required. Tables have been prepared for each of the chemical compounds of

interest. A large test kit will include a set of tables for determining the weight of the

chemical addition which will provide the desired increase in ppm for various pool

sizes.

Amount of Chemical Additions

The test results may indicate that certain additions are required to keep the pool

water in good balance. Using the tables from a test kit the amount of each addition

can be found for the size of the pool. Additions must be made one at a time and while

the pool water is circulating. Always allow time for one addition to disperse before

staring another. Always read the label and follow manufacturer's instructions before

adding a chemical to the pool.

After determining the amount of the addition it is always better to add only part

of it, especially if unsure of the pool capacity. Then the test can be run again and the

rest of the addition can be made as needed. Caution in making additions is always

advisable because it is easy to add more and impossible to remove over-additions.

The tables may give the addition amounts in either metric or standard

measures. A conversion table is given below for the amounts most commonly

encountered.

CONVERSION TABLE FOR LIQUID MEASURES

Milliliters (ml) Ounces (oz)

100 3.4

200 6.8

300 10.0

400 13.5

500 (half liter) 17.0 (about one pint)

1000 (one liter) 34.0 (about one quart)

3.785 liters (3785 ml) 128.0 (one gallon)

Pool Capacity

The size of a pool can be estimated in various ways. One way is to calculate

the volume based on the geometry. That is, multiply the average depth times the

surface area. For example, given a rectangular pool 18' x 36' with an average depth of

four feet the volume is 18 times 36 times 4 or about 2,600 cubic feet.

Once the volume is determined in cubic feet multiply by 62.3 pounds per cubic

foot for a pool capacity of 161,500 pounds. Dividing this by 8.3 pounds per gallon

gives 19,400 gallons. Or, combining the conversion factors, the volume in cubic feet

times 7.5 will give the pool capacity in gallons.

CONVERSION FACTORS FOR POOL CAPACITY

Pounds per gallon of water 8.3Pounds per cubic foot of water 62.3Gallons per cubic foot of water 7.5

For non-rectangular pools an estimate of the surface area is needed. One way

to do this is to draw on graph paper a scaled outline of the pool shape. Then count the

squares to estimate the area.

The easiest way to determine pool capacity is to check the water meter when

the pool is filled. This is the most accurate way to find the size in gallons. However,

there are not many occasions to do this.

A third method to estimate pool capacity is to note the effect of various size

additions on the increase in ppm. For example, if a ten pound addition of baking soda

gives only half the expected increase in ppm alkalinity then the pool capacity is

probably twice that expected. Additions of baking soda or calcium chloride can be

used to check on the estimated capacity.

/// PARTIAL DRAINING OF THE POOL \\\

Reasons to partially drain a pool are to reduce excessive stabilizer or dissolved

solids or to freshen the water. Over long periods dissolved organic material increases

especially if quaternary ammonium chlorides have been used.

Never completely empty a pool unless the ground water level has been

checked. If ground water is higher than the bottom of an empty pool it could lift out of

the ground. Many pools have a dry well underneath connected to a pipe used for

checking ground water and pumping it away.

/// OLD SCHOOL VS. NEW SCHOOL \\\

All of the above details about testing, adjusting and calculating additions of

chemicals are good things to know. But today many pool stores offer computer

analysis if you bring a water sample in. All you have to know is the temperature of the

pool and its capacity in gallons and the computer will do the analyses and calculate

the required additions. A word of caution: Not all store employees always know what

they are doing all the time. If you have doubts try bringing in samples of the same pool

water on different days or to different stores. There is always some variation in test

results because some of them are estimated or based on subjective judgments of color

or turbidity.

Obviously the sample water must be representative of the pool if the computer

aided analysis is to be meaningful. A clean sample container is a must and the

sample should be taken just prior to going to the store. Sometimes store employees

are too eager to recommend something be bought. You always have your own test kit

and the information provided in this manual to check on the recommendations. Again,

a good test kit with all the major tests is recommended for home use.

/// POOL WATER PROBLEMS \\\

Most problems will respond to shock treatment with liquid chlorine. It is an

inexpensive remedy worth trying before more drastic measures. Draining the pool,

refilling and balancing the water will take care of problems related only to the water.

For unusual problems involving equipment, the cement surface or the structure of the

pool seek the help of a professional pool service. company.

Algae

Even with regular preventive maintenance there can sometimes be algae

growth because chlorine levels are kept low for safety and economic reasons.

Chlorine and acid are the two items which deteriorate most rapidly. Weather

changes can hasten their disappearance. Since low chlorine or high pH results in

ineffective chlorination either can lead to algae growth. This is the most common

problem and is easy to solve. It is treated by super-chlorination or shock treatment as

described in the section CONTROL OF ALGAE.

Algae With High Chlorine

If chlorine is high and there is a lot of algae there could be two causes. The first

is high pH making the chlorine less effective. The second is too much cyanuric acid.

This condition, called "chlorine lock," makes super-chlorination or shock treatment less

effective. The cure is to lower the pH. If the algae persists, test the level of stabilizer --

if over 100 ppm partially drain the pool and add fresh water; if over 50 ppm do not use

stabilized chlorine for a few months.

Cloudy, Hazy Water

Cloudy water can have several causes. Among them are algae, high pH, high

alkalinity, high calcium, high combined chlorine or too much stabilizer or quaternary

ammonium chloride. Inert or inactive ingredients in solid chlorinating compounds can

cause cloudiness unless the filtering system removes them. Calcium hypochlorite can

cause temporary cloudiness. A tear in the filter will create cloudy water, especially if

diatomaceous earth is used.

To cure cloudy water first adjust the pH to 7.2 to 7.4. If cloudiness persists

check the filter pressure and clean the filter or change the DE. Check the filter for

holes if the DE appears to be leaking into the pool. Next super-chlorinate or shock

treat as required.

Also be sure the water is balanced with respect to calcium, carbonate and pH

for the given temperature. Cloudiness could occur during hot weather when rising

water temperature causes calcium carbonate to precipitate.

If the water is still cloudy it may be caused by small particles which pass through

the filter. These are suspended solids. The use of a flocculent (sequestrant) may be

required. This is a material which will cause suspended particles to clump together so

that the filter can remove them. A pool supply store will have one or more brands to

choose from.

Colored Water

Swimming pool water should be blue. When it appears to be a different color

there are two common causes. The first is algae which is discussed above. Algae

usually colors water green. The second is contamination with metal ions. This is an

infrequent problem. The color can vary depending on the metal which is present. Iron

and copper are the most common.

A first attempt to eliminate colored water should be to shock treat with chlorine

solution. If this is ineffective then a treatment to remove metal ions should be tried

next. Pool supply stores have products that will remove metal ions. Before treatment

have the water analyzed to identify the contaminant.

Foaming

Foaming is a problem that is usually caused by the over use of quaternary

ammonium chlorides. Waiting for the excess to dissipate is probably the best solution;

otherwise, it will be necessary to partially drain and refill with fresh water.

If foaming is caused by the presence of materials which do not belong in the

pool (like detergents) then it will be necessary to drain the pool to remove them.

Odors

If there is an unpleasant or strong odor from the pool water it is most likely from

the formation chloramines. This can be treated by chlorine shock which will eliminate

the combined chlorine. Chlorine treated water has a slight smell of chlorine. A strong

smell is often caused by urine, an amine, in the pool water combining with the chlorine

to form a chloramine.

High Dissolved Solids

This is a condition that will occur eventually. A side effect of buffering with

baking soda and acid is the formation of salt. The salt and other water treatment

compounds continue to accumulate in the pool water. It can be several years before

they become objectionable. The only way to reduce them is to partially drain the pool

and add fresh water. Flocculents will not eliminate dissolved solids.

High Filter Pressure

A sudden increase in filter pressure might be caused by an increase in pH

especially in hot weather. Precipitating calcium carbonate could plug the filter. Treat

this problem by adjusting the pH and cleaning the filter.

Rough Deposits On Pool Surfaces

If white crystalline deposits form on the cement surfaces it is usually caused by

high pH especially in hot weather. The high water temperature in combination with

high pH causes calcium to precipitate. The deposits usually scrape off easily and

when the pH is adjusted below 7.4 will dissolve.

In some cases the calcium content may have become too high. Stop using any

material which contains calcium. Adjust the pH and alkalinity to balance the calcium at

the present water temperature. In severe cases partially drain the pool and refill to

remove some of the calcium.

Cement Erosion

Cement erosion occurs if calcium dissolves from the cement. Neglecting it can

be very expensive. Its cause and cure are discussed below in the section on big

problems.

Staining of Cement

If a stain appears, which is a discoloration that does not brush off, it can usually

be removed by adding chlorine right near the spot. At the bottom of the pool this can

be done by placing one end of a pole near the stain and pouring liquid chlorine down

the other end. Follow it with a few cups of pool water to flush the heavier chlorine

solution out at the end of the pole near the stain. If you are not agile enough to do this

get someone else to help in order to avoid spilling chlorine on yourself. Do this with

the circulation turned off so that the water is still and leave it that way for a while.

Stains will often bleach out within a few minutes. Later on circulate the water and

adjust the pH if necessary in the usual way with an acid addition.

For intractable stains the advice of a pool professional may be necessary. He

may want to do tests to determine if there is something in the water such as metal ions

which should not be there.

/// HOW TO AVOID BIG PROBLEMS \\\

A pool with properly balanced water should last for a very long time -- at least

several decades. However, out of balance water can cause significant damage after

long exposure (about two years). The surface of the pool becomes pitted and rough.

The white finish cement may crumble and erode in patches down to the rough cement

below it. At this stage the calcium level may increase even though calcium is not

added. To repair such damage the pool is drained, resurfaced and refilled at a cost of

thousands of dollars.

Water can be out of balance when regular testing is not done for pH, alkalinity,

calcium and stabilizer. However, even with regular testing a situation can occur where

the water appears to be balanced but is not. The use of stabilized chlorine increases

the amount of cyanuric acid in the pool. This influences the alkalinity test. This

situation causes the pool water to appear balanced when in fact the carbon alkalinity

is actually very low. Total alkalinity will reflect the high stabilizer content and appear to

be normal. Unless this is recognized the water will become corrosive to the cement.

If water is left out of balance when refilling a pool it can cause serious problems

depending on the chemistry of the incoming water. See the section on "Incoming

Water Supply." A high pH may cause precipitation and staining of the cement if it is not

promptly adjusted.

To avoid these problems remember that:

1.) High levels of CYA stabilizer can result from continuous use of stabilized

chlorine (trichlor).

2.) The total alkalinity measurement has to be corrected if the stabilizer content is

high in order to know the true level of carbonate alkalinity.

3.) It is important to control water balance even when filling a pool.

/// ACHIEVING BALANCED POOL WATER \\\

The next two sections provide an overall view of how to put all the preceding

information together to achieve and maintain balanced pool water. To check the water

balance of a pool there are three major steps:

STEP ONE: Mechanical and Visual Inspection

1.) Make sure that the pump is operating.

2.) Check the flow rate of the water coming out of the return lines to the pool. Put

your hand in front of the water inlets to feel the force and direction of the water.

Redirect the water inlet jets as necessary for maximum circulation.

3.) Check the pressure of the filtering unit and compare it to the manufacturer's

recommended range. It may need cleaning.

4.) Look at the color and clarity. The water should be clear and blue -- deeper blue

at the deep end.

5.) Look for algae along the tile and on the walls and floor of the pool. It can

appear as a yellowish powder, dark green slime, or black spots.

5a.) If there is little or no algae omit STEP TWO and go to STEP

THREE and test the water.

5b.) Super-chlorinate if there is a small amount of algae. See the

section on CONTROL OF ALGAE.

5c.) For large amounts of algae use a shock treatment as described

below in STEP TWO.

STEP TWO: Shock Treatment (Only if required)

Add liquid chlorine to provide 30 to 60 ppm chlorine. This will be 5 to 10

gallons of ten percent liquid chlorine for a 15,000 gallon pool.

Run the pump and filter continuously until the water clears. This could take

several days and require cleaning the filter several times.

If this is your first experience with a pool it may be best to consult a pool care

service company if you are faced with very contaminated water.

After any required fixes to the equipment and brushing, filtering and vacuuming

and shock treatment with chlorine there are three questions to complete a visual

inspection: Is the water blue? Is it clear? Is it clean? When the water is blue, clear

and free of dirt or debris it is time to check for the things you can't see using the

chemical tests. It should also be odor free.

STEP THREE: Chemical Testing of the Water

1.) Sample the water and perform the tests for chlorine, pH, alkalinity, calcium and

stabilizer.

2.) Measure the water temperature.

3.) Compare the test results for all five tests to the ideal values.

4.) Make sure that the amount of cyanuric acid will not cause problems -- it should

be less than 40 ppm. If it is close to acceptable there is no need to adjust it

immediately. If it is over 100 ppm it will be necessary to partially drain the pool

and refill.

5a.) If calcium is below 200 ppm bring it to 300 ppm by adding calcium chloride.

5b.) If calcium is over 400 ppm use a nomogram or table to determine the

appropriate pH and alkalinity. Do not use the values given below.

6.) Adjust the chlorine concentration to about two ppm if it is low.

7.) Adjust the total alkalinity to about 90 ppm.

8.) Adjust the pH after making all the other adjustments. Keep it above 7.0 and

below 7.6 aiming for approximately 7.4.

The section on TESTING AND ADJUSTING POOL WATER contains useful

details for carrying out the above procedure. The test kit will contain the necessary

tables to find the amounts of the additions to bring the calcium, chlorine, alkalinity and

pH to the desired values in this order.

The sections on CALCIUM BALANCE and IDEAL CONDITIONS will provide

background information about balancing the chemicals for the water temperature.

The section on CHLORINATION provides descriptions of the various types of

chlorine compounds available. The choice will depend on the season, the calcium

hardness and the amount of stabilizer present.

/// MAINTAINING BALANCED POOL WATER \\\

Maintaining the chemical balance in pool water is a matter of making

adjustments for the decomposition of some of the chemicals and for seasonal changes

in temperature. There are many ways to accomplish this. The method described

below was selected for economy and convenience.

With proper filtration and with the water balanced with respect to pH, chlorine,

alkalinity, calcium and stabilizer the following procedures will then maintain the

balance.

Summer Procedures

1.) Use trichlor tablets for the four hottest months of the year. This will make it

easier to keep the chlorine level uniform and the pH stable. It will also provide

cyanuric acid (CYA) stabilizer during the season when the sunlight is most intense.

The three-inch tablet size is recommended for use with a floating dispenser to

provide the most reliable release rate of chlorine. From one to three tablets per week

should be used in a fifteen thousand gallon pool This is approximately forty to fifty

tablets per year (twenty pounds). A few can be reserved for use in midwinter to boost

the stabilizer level but the major portion will be required in the summer.

2.) When the chlorine requirements are not met by the trichlor tablets (at the

maximum rate of one tablet per 5,000 gallons per week) then use chlorine solution to

supplement the tablets.

3.) During the hottest season keep the pH around 7.3 and the carbonate alkalinity

around 80 ppm. Muriatic acid will be used to adjust the pH and baking soda will be

used to add carbonate alkalinity.

4.) Calcium should be kept near 300 ppm.

5.) After heavy use or rain or if algae is present super-chlorinate with liquid chlorine

by adding an additional 3 to 5 ppm over the usual level. If algae gets out of hand

shock treat with a large dose of liquid chlorine to obtain ten or more ppm.

6.) If there is algae on the tile chlorine solution can be poured along the perimeter

when the water is still and left overnight for maximum effect.

7.) If algae occurs on the bottom of the pool calcium hypochlorite powder can be

cast over the surface when the water is still and left overnight.

Off-Season Procedures

1.) During the cooler season it will be easier to maintain the water purity. In order

to allow the stabilizer concentration to drop use liquid chlorine only.

2.) This will require more frequent adjusting of the pH with acid. The pH can be

kept at about 7.5 and the carbonate alkalinity can be kept at about 100 ppm.

Off-Season Time Saver

For pools which remain open but unused during the winter there is a procedure

which will reduce some of the maintenance effort. If using chlorine solution change

the addition schedule as follows:

1.) Instead of one pint daily add about three quarts weekly.

2.) Adjust the pH to 7.4 with acid.

This is once-a-week super-chlorination. Select the amount so that at least one

ppm chlorine remains a week later. There will be a higher than necessary chlorine

level most of the time.

Testing for chlorine and pH can also be reduced to once a week. This time-

saving procedure replaces daily maintenance with testing and additions which can be

carried out on a weekend.

Preventive Maintenance for Away Time

During a period of time when regular maintenance will not be possible, such as

a trip away from home, preventive shock treatment will delay the onset of algae

growth. If the pool is to be unused keeping the chlorine at a higher than normal level

will prevent problems until regular maintenance can be resumed.

/// QUARTERLY TESTING TO MAINTAIN A BALANCED POOL \\\

The key to maintaining pool water is regular testing. And at least four times a

year all five chemical tests should be performed together. The cyanuric acid test can

be eliminated if the use of stabilized chlorine is limited. Be careful about choosing a

small test kit for just chlorine and pH. Some of them are either not reliable or difficult to

read precisely enough. Wrong information is just as bad as no information. There are

a few large test kits which are expensive but they contain everything you need to do a

complete analysis of your pool water. One of the best is "tailor made" for your pool.

This is the only brand name hint I've used. Try an internet search for test kits for pool

water and you will find them.

/// SEASONAL CHECK LIST \\\

Beginning of the Season, Opening the Pool:

1.) Clean the filter system.

2.) Shock treat.

3.) Test the calcium level and bring it to about 300 ppm.

4.) Check the level of stabilizer. It should be about 20 to 40 ppm.

5.) Test and adjust alkalinity and chlorine levels.

6.) Test and adjust the pH.

7.) Start using three-inch tablets of trichlor.

Summer:

1.) Increase the filtering/circulating time. See the section on "Pump Schedule" in

FILTERING.

2.) Use the trichlor tablets approximately one per week per 5,000 gallons.

3.) Use liquid chlorine for super-chlorination approximately once per week.

4.) Use powder chlorine for spot algae, only if necessary.

Off-Season:

1.) Reduce the filtering /circulating time or close the pool.

2.) Use weekly super-chlorination with liquid chlorine to reduce maintenance time.

/// CHEMICAL SUPPLIES \\\

The chemical supplies needed for the chlorination methods recommended in

this manual are listed below.

1.) Trichlor tablets Trichloro-s-triazinetrione, three-inch tablets, 99%

2.) Liquid chlorine Sodium hypochlorite, NaOCl, ten percent solution

3.) Muriatic acid Hydrochloric acid, HCl, 31.5%, concentrated, 20º Baume

4.) Baking soda Sodium bicarbonate, NaHCO3

5.) Calcium chloride Calcium dichloride dihydrate,CaCl2.2H2O, 80% (flakes) or 94% (pellets)

Four of them are needed on a regular basis: the tablets, liquid chlorine, acid

and baking soda. Item (5.) is not needed in hard water areas at all and for normal

water areas could be bought as needed since it is only used a few times a year.

Nothing else is required for normal maintenance based on chlorination.

I have not used brand names because it is the chemicals and their purity that is

important. Quite often they will be coming from the same manufacturing plant with

different packaging.

/// *KEY POINTS* ABOUT MAINTAINING POOL WATER \\\

1.) Liquid chlorine (sodium hypochlorite solution) is the most cost effective way to

chlorinate a pool.

2.) Trichlor tablets should be used for three or four months in summer. They

provide chlorination and cyanuric acid stabilizer.

3.) Cyanuric acid stabilizer should be kept around 50 ppm by limiting the amount of

trichlor used.

4.) The cement is preserved by balancing calcium and carbonate levels relative to

the water temperature and pH.

5.) Calcium chloride additions may be needed to keep calcium levels near 300

ppm.

6.) Total alkalinity should be about 90 ppm. The usual range is 70 to 130 and the

optimum depends on the water temperature.

7.) The optimum pH is 7.4 and is the single most important factor to control.

8.) Control of pH is achieved with hydrochloric (muriatic) acid and baking soda

(sodium bicarbonate).

9.) Algae can be controlled by manual brushing and periodic super-chlorination or

occasional shock treatment with chlorine solution.

10.) The best spot algaecide is calcium hypochlorite powder.

11.) A comprehensive test kit is necessary for maintaining balanced pool water.

Chemical adjustments based on regular testing will eliminate most problems.

12.) When purchasing supplies pay for the chemical compounds and not for brand

names. Check the labels for ingredients and the percent active. See the lists

for the necessary chemicals and price comparisons.

/// EQUIPMENT CHECK LIST \\\

* Calendar or Notebook

* Pool thermometer

* Floating dispenser for solid chlorine tablets.

* Adjustable length pole with pool brush, skimming net, vacuum head and hose.

* Hand brush with plastic or stainless steel bristles for cleaning the tile.

* Plastic one quart measuring cup with metric calibrations.

* Storage locker for chemicals.

* Petroleum jelly or silicone lubricant for O-rings.

* Water sample bottle for store analysis.

* Test kit for pH, chlorine, alkalinity, calcium and stabilizer including tables for

additions and a nomogram for water balance.

/// FILTERING \\\

Filtration and circulation are essential to good water maintenance. Algae and

debris are removed and the growth of algae is inhibited.

Cartridge Filters

Cartridge filters are commonly used in residential swimming pools to remove

solid debris from the water. As the cartridge picks up solid materials its effective pore

size becomes smaller. This results in higher pressure and decreased flow. When this

happens the pump must run longer to filter the same volume of water. The decreased

flow reduces the circulation in the pool and when it is too low the cartridge must be

removed and cleaned.

The usual routine for cleaning a cartridge filter is to take it apart and hose it

down. The same cartridge is then replaced in the filter housing and used again for

another cycle. The advantage of cartridge filters is the initial lower cost of the

equipment. The disadvantages are the inconvenience of the cleaning procedure and

eventual replacement cost of the cartridge element.

DE Filters

Diatomaceous earth (DE) filters are more effective than cartridge filters. The

result is cleaner water which looks much clearer.

These filters pull water through a fine powder suspended on a fabric. When the

filter pressure goes up the flow decreases and the powder has to be replaced with

fresh DE. For DE filters with a multi-port valve this procedure is quick and easy. The

used powder is blown off the fabric with pool water by setting the valve position to

"backwash." New DE powder is added through the skimmer with the valve in the

normal "filter" position.

At least once a year the filter element should be removed from the housing and

hosed down. This can be very easily done on a model with a clamp and O-ring seal

securing the cover.

The disadvantage of DE filters is higher initial cost. However, in the long run

they are cheaper than cartridge filters because the DE powder is inexpensive. (Note:

Sand filters are somewhere in between cartridge and DE filters in effectiveness and

cost.)

Pump Schedule

Filtering and circulating constantly would be best for the water quality but would

cost more and wear out the equipment sooner, especially the pump motor. As usual

there is a trade-off between cost, convenience and necessity. Less effective filtering

systems may have to run almost all day. A more expensive over-sized system will

allow for shorter running times and save a substantial amount of electricity. A timer is

essential for convenient scheduling. By alternating on and off periods the motor has a

chance to cool down and electricity can be saved without reducing the effectiveness.

Water temperature and amount of pool use need to be considered. When the

water temperature is above 85º F more filtering is needed than when it is below 60º F.

During the winter if the pool water is very cold very little circulation and filtration is

required and the pump can be scheduled to run for a few hours per day. Pools in a

cold winter climate do not need to be filtered until they are reopened.

/// BRUSHING AND VACUUMING \\\

Unless there is an automatic cleaner the sides and bottom of the pool should be

brushed occasionally. Use a pool brush with an adjustable telescopic pole. This will

dislodge debris which does not float. It also helps to prevent algae growth. Brushing

is more effective for removing algae than vacuuming. If there is algae to be removed

brush first to dislodge it and vacuum last. Brush debris toward the main drain. For

better suction at the drain during brushing close the skimmer line.

For debris which floats a hand held net can be used. A small hand brush is

needed to brush the tile and grout. For the spaces between tiles a toothbrush is very

effective.

A manual pool vacuum attachment connects to the skimmer outlet with a flexible

hose. It is used to remove debris which has sunk to the bottom of the pool. For

increased suction close down the main drain while vacuuming. Vacuum as required;

this will vary considerably depending on the pool location and enclosure. This chore

can be handled with an automatic cleaner. Automatic cleaners require maintenance

and cleaning themselves, so there is a trade-off here, not a completely hands-free

solution.

/// SKIMMER \\\

The simmer collects floating debris from the surface of the water. It does this by

pulling water over the edge of a floating weir and through a basket. (Some pools have

a fixed weir.)

The floating weir is the smaller upper part of the skimmer. It is designed so that

it will adjust to changes in water level. Once in a while a floating weir may become

stuck which causes air to be sucked into the pump. Simply dislodge the weir so that it

floats again. This is the reason for maintaining the water level at the midpoint of the

tile.

The floating weir usually has a pocket under its rim which has to be cleaned out

occasionally. The bottom section of the skimmer (the basket) should be periodically

removed and emptied. A screened-in pool will have less floating debris but an open

outdoor pools may have an occasional frog or mouse to remove. A daily check at least

is suggested in this case.

/// PUMP TRAP \\\

Most pumps for residential swimming pools have a trap to remove debris just

before the water enters the pump. This trap usually has a see-through cover. At least

every few weeks the cover should be removed when the pump is off to clean out the

basket inside. The frequency depends on whether a pool is screened-in or not. The

number of trees in the area also affects how much solid matter ends up in the trap

basket.

The cover to the trap filter should be replaced hand tight. It is a good idea to

lubricate the O-ring with petroleum jelly. A home-made wrench is very useful for

loosening the cover. The wrench can be made from a piece of 2"x6" lumber with a

notch cut in it to fit over the cover handle. Never use the wrench to tighten the cover to

avoid deforming the O-ring.

/// SAFETY \\\

The following reminders about the safe handling of pool chemicals should

always be observed.

* Always follow the manufacturer's instructions.

* Always read the label before use.

* Only add chemicals intended for swimming pools.

* Store pool chemicals in a secure place (child-proof).

* Never mix different chemicals together.

* Wait until one chemical addition is complete and has dispersed before making another.

* Dispose of empty containers after rinsing out with pool water. This puts all the material into the pool and keeps the trash barrel safe.

* Observe the precautions necessary for each type of chemical. Avoid skin contact, do not breathe the dust or fumes. Use rubber gloves, goggles or a dust mask as appropriate.

* Never add hazardous chemicals when the pool is in use.

* Do not use the pool until hazardous chemical additions have been dispersed.

Risks of Swimming In Chlorinated Water

Water has been chlorinated for drinking since the turn of the century. Generally

chlorine gas or liquid chlorine has been used. This results in the formation of

hypochlorous acid and hypochlorite ion as described in the section on

CHLORINATION. Studies of chlorinated drinking water have concluded the benefits

far exceed the risks.

With regard to swimming in chlorinated water there are several points to keep in

mind:

1.) The level of chlorine in swimming pools is about the same as, but can be higher

than, drinking water -- but not much higher when swimming is allowed.

2.) Swimming pool water is not intended to be ingested.

3.) The health consequences of not disinfecting water can be far more serious than

chlorine exposure.

4.) The use of chlorinated water in swimming pools has a long history -- about one

hundred years. No other method of water purification has been subjected to the

scrutiny that chlorination has or has been used on as wide a scale or for as long

a time.

Recently it has been learned that when water is chlorinated there may also be

traces of organochlorine compounds formed. Some of these are known to be

carcinogens (cause cancer). In spite of this the studies continue to find that drinking

chlorinated water is an acceptable risk.

As a practical matter when chlorinating swimming pool water the level of

chlorine should be kept as low as possible to avoid exposure risks. This also keeps

the cost lower. However, if the amount of chlorine is not sufficient then bacteria and

algae will flourish which is a health hazard. The cost of eliminating algae blooms and

excess bacteria is greater than the cost of routinely controlling them.

Safety and economics both argue for using a minimum level of chlorine. Small

and frequent additions of chlorinating compounds are less convenient but safer and

more economical. If a pool is not in use it is convenient to increase the chlorine level

with larger but less frequent additions of chlorine. See the section on "Adjusting

Chlorine" in TESTING AND ADJUSTING POOL WATER.

/// COST ANALYSIS \\\

When the methods described in this manual are used the amounts of chemical

supplies for maintaining 15,000 gallons for one year are approximately:

1.) Chlorine tablets: About 45 to 50 tablets (twenty-five pounds). This amount of

stabilized chlorine will provide chlorination for about five months and enough

stabilizer for one year.

2.) Chlorine solution: About 10 to 12 gallons per year to supplement the tablets

and for super-chlorination. And about seven gallons for shock, if needed.

3.) Calcium chloride: The amount will depend on the "hardness" of the water

supply. For soft water areas about 25 to 50 pounds per year should maintain

calcium at about 300 ppm.

4.) Hydrochloric (Muriatic) acid: About ten gallons per year to adjust the pH.

5.) Baking soda: About fifty pounds per year to adjust the alkalinity.

Notes on other optional materials:

Chlorine powder: About 12 pounds per year could be used as a spot algaecide

and for super-chlorination or shock, but only as an option, otherwise use another

seven gallons of liquid chlorine.

Algaecide: No additional algaecides should be required. The three forms of

chlorine listed above will take care of routine chlorination and super-chlorination and

shock treatments. See CONTROL OF ALGAE, Cost Comparison section.

Purchasing Chemical Supplies

See the two page chart PRICE COMPARISONS OF POOL CHEMICALS. The

relative prices for supplies are given. The actual dollar prices will vary depending on

the area. Note that the prices have been adjusted for the amount of active material. It

is important to check both the ingredients and the percent active material.

Buying in bulk or buying non-branded materials will reduce costs. This is

especially true for baking soda and calcium chloride flakes. The price of some

chlorine compounds is more sensitive to quantity than others. Calcium hypochlorite

(dry chlorine) will be much cheaper in drums. Packaging also affects price so single

pound packs cost less than pails on a per pound basis.

The chemical effectiveness is important in some cases. Dry acid is not only

more expensive but it is less effective so more of it must be purchased to replace a

given weight of muriatic ace. One major money saving strategy is to use liquid

chlorine for super-chlorination and shock treatment to prevent algae growth. The cost

of exotic algaecides is often $50 per gallon; this is why they are usually sold by the

pint or quart.

Some treatments for algae are just small packages of the usual chlorinating

compounds disguised with clever brand names. A gallon of liquid chlorine will out

perform them at a fraction of the cost.

Costs of Testing

The cost of testing will average $15 per year. A complete test kit costs about

$65 and will last for several years. Replacing reagents will cost about $20 to $25 per

year.

Summary of Estimated Annual Costs (for a 15,000 gallon pool)

Chlorine tablets $60 to 80

Chlorine solution $70 to 100

Acid $ 50 to 75

Baking soda $ 30 to 50

Calcium flakes $ 0 to 30

Test kit supplies $ 20 to 30

YEAR'S TOTAL $ 230 to 365

These costs are estimated for an area where there is competition among

suppliers and they include sales taxes of seven percent. Your costs may be lower but

should not have to be higher than these unless you are in an area where pool

supplies are not commodity items.

This is about $15 per thousand gallons per year. A ten thousand gallon pool

would cost about $150 per year to maintain and a twenty thousand gallon pool should

cost about $300 per year.

PRICE COMPARISONS OF POOL CHEMICALS -- CHLORINE COMPOUNDS

Chlorine compound: Relative Prices Per Pound, Active:

Sodium hypochlorite

2.5 gallon bulk solution 1.00

one gallon prepackaged 1.70

Trichlor tablets * 2.50

Calcium hypochlorite **

envelopes 1.50

pail 3.00

drum 1.75

Lithium hypochlorite 20.00

Dichloro-s-triazinetrione 4.50

Notes:* Trichlor requires less acid for pH adjustment and it includes stabilizer (cyanuric

acid) which offsets the price compared to other sources of chlorination.

** Calcium hypochlorite chlorinates and provides calcium so less calcium chloride will be required.

PRICE COMPARISON OF POOL CHEMICALS -- OTHERS

Relative Prices Per Pound of Active Material

Compounds for pH control:

Muriatic acid (HCl) 0.50

Sodium bisulfate (Dry acid) # 0.95

Sodium bicarbonate (baking soda), bulk 0.35

Sodium bicarbonate, small package 1.00

Sodium carbonate (soda ash) ## 0.80

Other compounds:

Calcium chloride, unbranded, bulk 0.50

Calcium chloride, specialty brand 1.15

Quaternary ammonium chlorides 4.50

Cyanuric acid (stabilizer) 2.25

Notes:# Dry acid is less effective on a weight basis by a factor of three making muriatic acid five times more cost effective.

## Baking soda provides more carbonate on a weight basis than soda ash so it is a more effective buffering agent. This increases its price advantage. However, for acid absorption to raise pH, soda ash is more effective but not enough to offset the higher price.

POOL CHEMICAL DATA SHEET

Name(s): Sodium hypochloriteChlorine solutionLiquid chlorineNaOCl

Type of Compound: Chlorine source, liquid

Description: Ten percent solution in waterYellowish liquid, similar to bleachIrritant -- avoid contactOxidizerCorrosive -- handle with cautionLimited shelf life

POOL USE:Source of chlorine (hypochlorous acid) for routine chlorination, super-chlorination and shock treatment.The most cost effective algaecide available.Causes pH to increase.

Caution: Liquid chlorine is corrosive and must be handled with care.

Alternate: Calcium hypochlorite

RECOMMENDATION: Sodium hypochlorite is recommended as the most cost

effective source of chlorine.

POOL CHEMICAL DATA SHEET

Name(s): Trichloro-s-triazinetrioneTrichlorChlorine tabletsTrichloroisocyanuric acid

Type of Compound: Chlorine source, solid, contains stabilizer (cyanuric acid)

Description: Tablets, three-inch diameter, white Also in smaller tablet sizes, sticks and granules99% active, 89% available chlorine

POOL USE:Source of chlorine (hypochlorous acid) for routine chlorination and super-chlorination.Source of stabilizer (cyanuric acid).Does not upset pH.

Caution: Continuous use of trichlor can result in excessive build-up of CYA stabilizer.

Alternate: Sodium hypochlorite solution and cyanuric acid crystals.

RECOMMENDATION: Trichlor three-inch tablets are recommended as a cost effective

source of chlorine and stabilizer.

POOL CHEMICAL DATA SHEET

Name(s): Calcium hypochloriteDry chlorineChlorine powderGranular chlorineCa(OCl)2 or Ca (ClO)2

Type of Compound: Chlorine source, solid, contains calcium

Description: White solidGranules, powder, tablets or cartridgesOxidizerIrritant -- avoid contact65% active, 35% inert (sometimes 75/25)65% available chlorine

POOL USE:Source of chlorine (hypochlorous acid) for routine chlorination, super-chlorination and shock treatment.An effective algaecide.An excellent spot algaecide.Causes pH to increase.Also provides calcium.A solid alternative to liquid chlorine for easier handling.

Caution: Should not be used in pools with hard water problems. Continuous use will add about 250 ppm calcium per year.

Caution: The inert material may give the water a cloudy appearance until it is removed by filtering.

Alternate: Sodium hypochlorite

POOL CHEMICAL DATA SHEET

Name(s): Lithium hypochloriteLi (OCl) or Li (ClO)

Type of Compound: Chlorine source, solid

Description: White powderOxidizerIrritant -- avoid contact, do not breathe the dust70% inert

POOL USE:Source of chlorine (hypochlorous acid) for routine chlorination, super-chlorination or shock treatment.Causes pH to increase.Does not add calcium or stabilizer.Easier to handle than liquid chlorine.An expensive alternative source of chlorine.

Alternate: Sodium hypochlorite

POOL CHEMICAL DATA SHEET

Name(s): Sodium dichloro-s-triazinetrione dihydrateDichlor

Type of Compound: Chlorine source, solid, contains stabilizer (cyanuric acid)

Description: White granules99% activeIrritating -- avoid breathing the dustOxidizer

POOL USE:Source of chlorine (hypochlorous acid) for routine chlorination, super-chlorination or shock treatment.Source of stabilizer (cyanuric acid)

Caution: Should not be used if cyanuric acid levels are high.

Alternate: Trichloro-s-triazinetrione

NOT RECOMMENDED because it contains less chlorine and more stabilizer than

trichlor.

POOL CHEMICAL DATA SHEET

Name(s): Hydrochloric acidMuriatic acidHCl

Type of Compound: For control of pH. It lowers pH.

Description: Solution of acid in water, concentrated, 20º Baume, 31.5%Corrosive -- avoid contactIrritating -- avoid breathing fumes

POOL USE:Lowers pH.

Caution: Acid solution is corrosive and must be handled with care.

Alternate: Sodium bisulfate

RECOMMENDATION:

Hydrochloric (muriatic) acid is recommended as a cost effective method for

lowering pH. It is five times more cost effective than sodium bisulfate.

POOL CHEMICAL DATA SHEET

Name(s): Sodium bisulfateDry acidSodium hydrogen sulfateSodium bisulfate mono-hydrateNaHSO4

Type of Compound: For control of pH. It lowers pH.

Description: White powderCorrosive -- avoid contactHygroscopic -- absorbs moisture

POOL USE:Lowers pH.A solid alternative to liquid acid easier to handle and store.

Alternate: Hydrochloric acid (muriatic acid)

POOL CHEMICAL DATA SHEET

Name(s): Sodium bicarbonateBaking sodaSodium hydrogen carbonateNaHCO3

Type of Compound: For control of pH. It raises the pH. For buffering. It stabilizes the pH. Source of carbonate ions for cement stability.

Description: White powder. Other uses include cooking, cleaning, deodorizing and medication as an antacid.

POOL USE:Baking soda slows down changes in pH.It also prevents the cement from dissolving.It can be used to adjust pH to higher, more basic values.

RECOMMENDATIONS:Baking soda is recommended as a cost effective source of carbonate to buffer the pH and preserve the cement.

Alternate: Sodium carbonate (soda ash)

POOL CHEMICAL DATA SHEET

Name(s): Sodium carbonateSoda ashSodium sesquicarbonateNa2CO3 or Na2.NaHCO3.2H2O

Type of Compound: For control of pH. It raises pH. A source of carbonate ions for cement stability.

Description: White powder, granular

POOL USE:It can be used to raise pH. It is useful when the pH is very low.It can be used to raise carbonate alkalinity. However, the percentage by weight of carbonate is greater in baking soda.

Alternate: Baking soda (sodium bicarbonate)

POOL CHEMICAL DATA SHEET

Name(s): Calcium chlorideCalcium dichlorideCalcium dichloride dihydrateCaCl2.2H2O

Type of Compound: Calcium source

Description: Solid, white, flakes or pelletsHygroscopic -- absorbs moistureIrritant -- avoid contact80% calcium chloride plus 20% other chlorides; can be up to 94% Ca

POOL USE:A source of calcium to balance the solubility of the calcium in the cement.

Caution: Too much calcium will result in rough deposits on the pool surfaces.

Caution: Too little calcium will allow the cement to dissolve.

RECOMMENDATION: Bulk calcium chloride is recommended as a cost effective

source of calcium.

POOL CHEMICAL DATA SHEET

Name(s): Quaternary alkyl ammonium chloridesUsually a mixture of several compounds within this chemical family.For example: n-alkyl dimethyl benzyl ammonium chloride

n-alkyl dimethyl ethylbenzyl ammonium chloride

Type of Compound: Algaecide

Description: Ten percent solution in water

POOL USE:

An effective algaecide chemically different from chlorination.An optional routine treatment for inhibition of algae growth.

Caution: Too much quaternary ammonium chlorides will cause foaming.

Not recommended.

POOL CHEMICAL DATA SHEET

Name(s): Cyanuric acidCYAStabilizerWater conditioner1,3,5-triazine-2,4,6--triol

Type of Compound: Chlorine stabilizer

Description: Solid, white, flakes or granulesIrritant -- avoid contactHygroscopic -- absorbs moisture

POOL USE:Cyanuric acid at 20 to 40 ppm extends the lifetime and effectiveness of chlorine by protecting it from degradation by the ultra-violet rays of the sun.

Caution: Too much cyanuric acid will inhibit the effectiveness of chlorine.

Caution: Too much cyanuric acid will mask a deficiency in carbonate alkalinity by increasing the total alkalinity.

Alternate: Stabilized chlorine (trichloro-s-triazinetrione)

SUMMARY OF POOL CHEMICALS AND RECOMMENDED USES

Sodium hypochlorite Recommended for chlorination, super-chlorination and shock treatment.

Trichloro-s-triazinetrione Recommended for chlorination and as a source of stabilizer.

Calcium hypochlorite Alternate source of chlorine and calcium. Recommended as a spot algaecide.

Lithium hypochlorite Alternate source of chlorine. Expensive.

Sodium dichloro-s- Not recommended for routine use.triazinetrione

Hydrochloric acid Recommended for lowering pH.(Muriatic acid)

Sodium bisulfate Alternate for lowering pH.(Dry acid)

Sodium bicarbonate Recommended for buffering pH and as a source of (Baking soda) carbonate.

Sodium carbonate Alternate source of carbonate. Can be used if(Soda ash) large increases in pH are needed.

Calcium chloride Recommended source of calcium.

Alkyl ammonium chlorides An optional routine algaecide.

Cyanuric acid Alternate source of stabilizer.

/// QUIZ \\\

1. THE AMOUNT OF ACTIVE CHLORINE IN YOUR POOL DEPENDS ON:

A. THE WATER TEMPERATURE

B. THE ALKALINITY

C. THE pH

2. TO PREVENT CORROSION OF CEMENT POOLS ADD:

A. CALCIUM AND STABILIZER

B. STABILIZER AND BAKING SODA

C. CALCIUM AND BAKING SODA

3. THE BEST MATERIAL FOR CONTROLLING ALGAE IS:

A. QUATERNARY AMMONIUM CHLORIDE SOLUTION

B. COPPER CONTAINING ALGAECIDE SOLUTIONS

C. SODIUM HYPOCHLORITE SOLUTION

4. A CEMENT POOL SURFACE SHOULD LAST:

A. THREE YEARS

B. SEVEN YEARS

C. WELL OVER TEN YEARS

ANSWERS: In each case the correct answer is C. Not knowing these answers can

lead to increased costs, algae problems or expensive repairs.