WATER PIPING DESIGN FOR A RESIDENCEWATER PIPING DESIGN FOR A RESIDENCE

In the packet is a floor plan of a residence with In the packet is a floor plan of a residence with water supply piping shown. Follow the process water supply piping shown. Follow the process as a step by step procedure for the proper as a step by step procedure for the proper method of selecting sizes for a water supply method of selecting sizes for a water supply system.system.

First, as in any design, start with a floor First, as in any design, start with a floor plan. Indicate the plumbing fixtures that will plan. Indicate the plumbing fixtures that will require water, and indicate the fixture unit require water, and indicate the fixture unit demand for each fixture. demand for each fixture.

Fixture Unit Value

= fixture units

= gpm

bathtub

wc

lavatory

2Hose bibb

Fixture

bath tublavatory

sinkshower

automatic washer

water closet1

2

32

2

3

HB heaterwater

sinkshr

autowash

wc

lav

HB

Connect all the fixtures with a line that will Connect all the fixtures with a line that will represent cold water piping, then extend the line represent cold water piping, then extend the line to the logical location of a water source.to the logical location of a water source.

The cold water lines in this illustration will The cold water lines in this illustration will be shown green in color.be shown green in color.

Indicate dimensions as necessary to Indicate dimensions as necessary to determine the longest distance water will have to determine the longest distance water will have to travel from source to farthest fixture. Show travel from source to farthest fixture. Show pertinent information for piping such as available pertinent information for piping such as available pressure, meter, rise, fittings, and valves.pressure, meter, rise, fittings, and valves.

Connect the cold water line to the water Connect the cold water line to the water heater. heater.

The entrance water line should be located The entrance water line should be located somewhere near the most dense concentration of somewhere near the most dense concentration of fixtures.fixtures.

bathtub

= fixture units

= gpm

waterHB heater

sink

20

'-0"

autowash

shr

wc

lav

2Hose bibb

wclavatory

35'-0"

water closet

automatic washer

showersink

lavatorybath tub

Fixture Fixture Unit Value

2

322

31

12

'-0"

HB

main valve

pipe rises 10'

60

'-0"

60 p.s.i. pressurewater meter

The next step is to indicate the requirement The next step is to indicate the requirement for supply in fixture units for EACH SEPARATE for supply in fixture units for EACH SEPARATE SEGMENT OF PIPE from the farthest fixture to the SEGMENT OF PIPE from the farthest fixture to the source of water. source of water.

Then with the fixture unit / gallons per Then with the fixture unit / gallons per minute conversion chart, determine the required minute conversion chart, determine the required gpm for each segment of pipe.gpm for each segment of pipe.

Realize that the water does not have a Realize that the water does not have a fixture unit value, hence it does not consume fixture unit value, hence it does not consume water. It merely takes some of the cold water water. It merely takes some of the cold water and heats it for use in fixtures that supply hot and heats it for use in fixtures that supply hot water. The fixture unit value for the pipes in and water. The fixture unit value for the pipes in and out of the water heater will be the sum of the out of the water heater will be the sum of the fixtures that supply hot water. fixtures that supply hot water.

8

7gpmbath

= fixture units

= gpm

tub

20

'-0

"

2Hose bibb

wc5

fu

5

gpmfu

fu

gpmlavatory 6

5 1

2'-0

"

22

35'-0"

HB

automatic washer

Fixture Unit ValueFixture

bath tubshowersink

water closetlavatory

2

322

31

60

'-0

"10

waterHB heater

wc

9

washauto

shr

11

sink

10 13

2

211

lav

fu

gpm13

21

15

main valve

pipe rises 10'

60 p.s.i. pressurewater meter

21

15

The next step is to connect all fixtures that The next step is to connect all fixtures that will be supplied with hot water with a line to will be supplied with hot water with a line to represent hot water piping. Connect the line to represent hot water piping. Connect the line to the water heater. the water heater.

10gpmbath

10

HB

= gpm

= fixture units

tub2

0'-0

"

waterheater

sink

112

2

13autowash

shr

119

wc

lav

main valve

2Hose bibb

wclavatory

fu

5

5

35'-0"

fu gpm

5

6gpm

fu

22

12

'-0

"

fu

gpm7

8

HB

Fixture Unit ValueFixture

automatic washer

water closet

bath tub

sinkshower

lavatory2

22

3

13

60

'-0

"

13

15

21

pipe rises 10'

60 p.s.i. pressure

15

21

water meter

Indicate the fixture unit value for each Indicate the fixture unit value for each segment of pipe from the farthest fixture to the segment of pipe from the farthest fixture to the water heater. water heater.

Then with the conversion chart, indicate the Then with the conversion chart, indicate the gpm demand for hot water for each segment of gpm demand for hot water for each segment of pipe in the hot water service. pipe in the hot water service.

13

10

21

15

21

15

pipe rises 10'

bath gpmtub

HB

fu

gpm

= fixture units

= gpm

3

320

'-0"

sink

10 13

2

2

119

87

water closet

automatic washerHose bibb

shower

lavatorybath tub

Fixture

wc

sink

2

fu

lavatoryfu

5

5 5

6 fugpm

2

35'-0"

gpm

12

'-0"

gpm

8 fu

7

2

HB

main valve

Fixture Unit Value

2

3

22

31

60

'-0"

waterheater

auto

11

wash

shr

11

wc

9

lav

60 p.s.i. pressurewater meter

In the calculation of fixture units for In the calculation of fixture units for segments of pipes to fixtures, realize this segments of pipes to fixtures, realize this condition:condition:

Imagine a sink. Turn on hot water only. All Imagine a sink. Turn on hot water only. All the water comes out of the hot water pipe. Now the water comes out of the hot water pipe. Now turn off hot and turn on cold water fully. All the turn off hot and turn on cold water fully. All the water comes out of the cold water pipe – the water comes out of the cold water pipe – the same volume as the hot water.same volume as the hot water.

Now turn hot half on, and cold half on. The Now turn hot half on, and cold half on. The same volume, except half comes from hot and same volume, except half comes from hot and half comes from cold. half comes from cold.

This is to illustrate that the water heater This is to illustrate that the water heater does not contribute to fixture unit count. Water does not contribute to fixture unit count. Water to a fixture comes from either a cold pipe or a hot to a fixture comes from either a cold pipe or a hot pipe, or a mixture. pipe, or a mixture.

15

21

pipe rises 10'

15

21

10

13

35'-0"

wc

tubbath

HOT sink

20

'-0"

= fixture units

= gpm

HB

WATER "B"

2

2

11

13

9

10

gpm

fu

fulavatory

gpm

5

5

3

5

6gpm

fu

3

2fu

WATER "A"COLD

7

fu8

gpm

87

12

'-0"

gpm2

HB

main valve

Fixture

bath tublavatory

shower

Hose bibbautomatic washer

water closet

sink

Fixture Unit Value

2232

213

60

'-0"

waterheater

11

auto

shr

wash

lav

9

wc

11

water meter60 p.s.i. pressure

The next step is to determine the measured The next step is to determine the measured length of pipe from the water source to the fixture length of pipe from the water source to the fixture farthest away from the source. farthest away from the source.

It is rather apparent that the longest length It is rather apparent that the longest length of travel for water is from the source, into the of travel for water is from the source, into the building to the water heater, then from the water building to the water heater, then from the water heater to the bath room on the left side of the heater to the bath room on the left side of the plan. plan.

The dimensions from the source = 60’ + 12’ The dimensions from the source = 60’ + 12’ + 20’ to the water heater, then back 12’ + 35’ to + 20’ to the water heater, then back 12’ + 35’ to the left side bath room, which totals 139 feet, the left side bath room, which totals 139 feet, measured length. Then realize equivalent length measured length. Then realize equivalent length for fittings cannot be added because the pipe for fittings cannot be added because the pipe sizes are not known, so take half the measured sizes are not known, so take half the measured length as an allowance for equivalent length of length as an allowance for equivalent length of fittings, and add it back to the measured length fittings, and add it back to the measured length making;making;

139’ + 69’ = 208’ equals calculated length, 139’ + 69’ = 208’ equals calculated length, which means in essence, the available pressure which means in essence, the available pressure must be able to push water through 208 feet of must be able to push water through 208 feet of straight pipe with no fittings. straight pipe with no fittings.

Next, determine the available pressure, Next, determine the available pressure, setting aside allowances for pressure for meter, setting aside allowances for pressure for meter, for rise, and for fixtures.for rise, and for fixtures.

See that the total amount of water required See that the total amount of water required for the system is 15 gpm. Go to the water meter for the system is 15 gpm. Go to the water meter chart and find at the bottom, 15 gpm. From there chart and find at the bottom, 15 gpm. From there move straight up the chart until it intersects the move straight up the chart until it intersects the middle meter size, which is ¾”.middle meter size, which is ¾”.From that intersection, read directly to the left From that intersection, read directly to the left and and see that it takes 5 psi to operate the ¾” see that it takes 5 psi to operate the ¾” meter. meter.

Next, the supply pipe rises 10’, so the Next, the supply pipe rises 10’, so the pressure required to raise water 10’ = .433 x 10 = pressure required to raise water 10’ = .433 x 10 = 4.33 psi.4.33 psi.

Then allow 15 psi to operate fixtures.Then allow 15 psi to operate fixtures.So total amount lost to the total pressure So total amount lost to the total pressure

equalsequals

6060 – 5– 5 – 4.33– 4.33 – 15– 15 = 35.67 psi that is available = 35.67 psi that is available to push the water through the system.to push the water through the system.

So, at this point remains 35.67 psi pressure So, at this point remains 35.67 psi pressure to push the water a distance of 208 feet.to push the water a distance of 208 feet.

From that, convert the amount of From that, convert the amount of pressure pressure per 100 feet of length;per 100 feet of length;

[[ 35.67 35.67 / 208 ] x 100 = / 208 ] x 100 = 17.1517.15 psi per psi per 100 feet 100 feet

Then do not allow water in the system to Then do not allow water in the system to travel faster than 8 feet per second.travel faster than 8 feet per second.

On the pipe size chart, find 17.15 at the On the pipe size chart, find 17.15 at the bottom, draw a line straight up until it intersects bottom, draw a line straight up until it intersects the 8 fps line. Then where each pipe diameter the 8 fps line. Then where each pipe diameter intersects either the VERTICAL line or the 8 FPS intersects either the VERTICAL line or the 8 FPS line, read to the left and determine the maximum line, read to the left and determine the maximum gpm each pipe diameter will supply.gpm each pipe diameter will supply.

Make a small chart. Make a small chart.

Pipe dia. GPMPipe dia. GPM½”½” 33¾” ¾” 991”1” 18181 ¼”1 ¼” 28281 ½”1 ½” 4444

Use this chart to show diameter for each Use this chart to show diameter for each segment of pipe in the system, based on the segment of pipe in the system, based on the required gpm for each.required gpm for each.

Now verify the assumption of water meter size: See Now verify the assumption of water meter size: See that the total demand for the building is 15 gpm. that the total demand for the building is 15 gpm. From the pipe chart above, see that a 1” pipe is From the pipe chart above, see that a 1” pipe is required to supply 15 gpm based on the criteria. So required to supply 15 gpm based on the criteria. So a 1” meter is required. From the water meter a 1” meter is required. From the water meter chart, see that a 1” meter requires less than 2 psi chart, see that a 1” meter requires less than 2 psi to provide 15 gpm, so the 5 psi allowance was OK.to provide 15 gpm, so the 5 psi allowance was OK.

Next was an assumption for equivalent length of Next was an assumption for equivalent length of fittings, in which we allowed 69 feet. From the fittings, in which we allowed 69 feet. From the plan begin at the source (meter) and follow along plan begin at the source (meter) and follow along the path of pipe of the longest length and list the the path of pipe of the longest length and list the fittings and size, since you now know the pipe fittings and size, since you now know the pipe diameters. Then tally the length:diameters. Then tally the length:

Since the actualSince the actualequivalent length of fittingsequivalent length of fittingsamounts to only 21 feet, theamounts to only 21 feet, theallowance of 69 feet in theallowance of 69 feet in thecalculation was sufficient.calculation was sufficient.

3/4" side T = 4.0 ft= 5.0 ft

= 2.0 ft= 0.6 ft

20.6 ft

= 0.6 ft3/4" ell x 2

1/2" inline T

total equivalentlength =

1/2" inline T1/2" ell

= 0.6 ft= 6.0 ft= 1.8 ft

actual equivalentlength of fittings

1" ell x 21" inline T x 2

1" valve