T W Testing the Double Check Valve Assembly I n s i d e C r o s s T a l k Testing the Double Check • New Members Training Schedule • Manual Update Manual Update continued on page three S p r i n g 2 0 0 1 continued on page four he Manual Review Commit- tee continues to work towards the completion of the Tenth Edition of the Manual of Cross-Connection Control. As mentioned in previous articles the organization of the manual will be slightly different. The Sections will be outlined as follows: Objectives 1. Definitions 2. History/Introduction 3. Hydraulics 4. Elements of a Program 5. Cross-Connection Control Practice—Surveys 6. Facilities 7. Equipment 8. Sample Letters, Forms, Installa- tion Guidelines, Model Ordi- nance 9. Field Test Procedures 10. Specifications for Backflow Preventers 11. Summary of Case Histories Sections two and three are essen- tially new to the Manual. A history has not been included in previous editions of the Manual; however, the committee felt that it would be beneficial for end users to have a brief history of cross-connection control, along with an introduction to the topic. The introduction will clarify some of the definitions and bring the reader up to speed on the basics of backflow and cross-connec- tion control. This is one area where the Manual has lacked in previous editions. This combined with the following section on hydraulics will make the Manual a complete source for training courses which cover, not hen field testing the double check valve assembly, one obtains a reading on the first check valve and then takes a reading on the second check valve. In most cases, the tester may continue on to test the second check valve after testing the first check valve, even if the first check valve holds at a value below the minimum value of 1.0 psi. The exception to this is when the reading on the number one check valve is less than 1.0 psi AND the No. 1 shutoff valve leaks. Under these conditions, repairs must be made before continuing on to test the No. 2 check valve. The Ninth Edition of the Manual of Cross-Connection Control, in Section 9.3.3.2, Test T2, states: After adjusting the bleed-off valve so that there is a slight drip at the No. 3 test cock, record the reading on the gage as the static pressure drop across the No. 1 check valve. This reading should be greater than or equal to 1.0 psi…if the reading is less than 1.0 psi, the No. 1 check valve must be repaired and retested before proceeding to test No. 2. What many testers don’t understand is why the test must be stopped at this point to repair the check valve, when at other times the tester may go on and test the second check valve. One needs to look at the entire test in order to understand the reasoning.
Transcript
T W
Testing the DoubleCheck ValveAssembly
I n s i d e C r o s s T a l kTesting the Double Check • New Members
Training Schedule • Manual Update
Manual Update
continued on page three
S p
r
i n
g
2
0
0
1
continued on page four
he Manual Review Commit-tee continues to work towards thecompletion of the Tenth Edition ofthe Manual of Cross-ConnectionControl. As mentioned in previousarticles the organization of themanual will be slightly different.The Sections will be outlined asfollows:
Objectives1. Definitions2. History/Introduction3. Hydraulics4. Elements of a Program5. Cross-Connection Control
9. Field Test Procedures10. Specifications for Backflow
Preventers11. Summary of Case Histories
Sections two and three are essen-tially new to the Manual. A historyhas not been included in previouseditions of the Manual; however, thecommittee felt that it would bebeneficial for end users to have abrief history of cross-connectioncontrol, along with an introduction tothe topic. The introduction willclarify some of the definitions andbring the reader up to speed on thebasics of backflow and cross-connec-tion control. This is one area wherethe Manual has lacked in previouseditions. This combined with thefollowing section on hydraulics willmake the Manual a complete sourcefor training courses which cover, not
hen field testing thedouble check valve assembly, oneobtains a reading on the first checkvalve and then takes a reading onthe second check valve. In mostcases, the tester may continue on totest the second check valve aftertesting the first check valve, even ifthe first check valve holds at a valuebelow the minimum value of 1.0 psi.The exception to this is when thereading on the number one checkvalve is less than 1.0 psi AND theNo. 1 shutoff valve leaks. Underthese conditions, repairs must bemade before continuing on to testthe No. 2 check valve.
The Ninth Edition of the Manual ofCross-Connection Control, in Section9.3.3.2, Test T2, states:
After adjusting the bleed-offvalve so that there is a slight dripat the No. 3 test cock, record thereading on the gage as the staticpressure drop across the No. 1check valve. This reading shouldbe greater than or equal to 1.0psi…if the reading is less than1.0 psi, the No. 1 check valvemust be repaired and retestedbefore proceeding to test No. 2.
What many testers don’t understandis why the test must be stopped atthis point to repair the check valve,when at other times the tester maygo on and test the second checkvalve. One needs to look at theentire test in order to understandthe reasoning.
T he Foundation’s Membership Program provides many benefits to the Membersof the Foundation. These include: twenty percent discounts on FoundationTraining courses for any employee of the Member company/organization, the Listof Approved Backflow Prevention Assemblies, printed quarterly, and access to the up-to-the-minute version of the List for those Members with Internet access.
Members are encouraged to call the Foundation with technical questions. TheFoundation’s Engineering Staff is available to assist Members with the variousaspects of field testing backflow preventers, installing backflow preventers,administering their cross-connection control program.
Mailing Address:Foundation for Cross-Connection Control andHydraulic ResearchUniversity ofSouthern CaliforniaKaprielian Hall 200Los Angeles, CA 90089-2531
The Foundation acceptsPurchase Orders via mail orfax and credit card orders(Visa, MasterCard, Discover)via telephone and the Web.
Alaska, State ofAndermac Inc.Andersen Commercial Plumbing, Inc.Anderson Mechanical SystemsAndrews, City ofBackflow Tests, by GeorgeBakflo Tek Inc.Baldy Fire and SafetyBessinger’s Backflow Service, LLCBig Bear Lake, City ofBozeman, City ofCross Connection ManagementCurb Box SpecialistsD & D Plumbing, Inc.Dale BoyerDifferential Pressure PlusEnvironmental Training Associates ConsultngFt. Worth WaterHanol Corp., Ltd.Hawaii Pacific Engineers, Inc.Kannah Creek Water PlantLongwood, City ofMcDaniel Fire Systems, Inc.Mueller GroupMurrieta County Water DistrictOak Ridge National LaboratoryPacific Backflow CompanyPacific City Joint Water Sanitary AuthorityPenn State - HarrisburgPlumbers & Steamfitters Training CenterRound Hill General Improvement Dist.Sacramento Flow ControlSan Antonio Water SystemSan Marino, City ofSanta Ynez River Water Conserv.Shade Mech. Inc.Southern Illinois UniversitySprinkler Fitters JATCTomlin’s Backflow Testing & RepairTumwater, City ofU. S. Marine CorpsUniversity of Nevada - RenoWaxahachie, City ofWest Wilson Utility Dist.Weston, Benshoof, et alWTI Training Group
only testing, but general cross-connection control topics as well.
A summary of some of the itemsdiscussed for the Tenth Edition ofthe Manual follows. Some of theitems, the Manual Review Com-mittee (MRC) is still considering.Some have been rejected or ac-cepted. Comments and sugges-tions are welcome and encouraged.It is the goal of the MRC to makethe Tenth Edition as useful aspossible to the end user, so pleasesubmit suggestions to the MRC viathe web page at http://www.usc.edu/fccchr/mrc/ or bysending them to the MRC care ofthe Foundation office.
One of the first items the MRClooked at was adding a representa-tive of the Backflow PreventionManufacturer’s Association to theManual Review Committee. Thiswas approved at one of the firstmeetings. The BPMA representa-tive participates in all the meetings,but is a non-voting member. Thisaction helps the MRC to see theperspectives of the manufacturerswhen considerations arise for thebackflow prevention assemblystandards. Historically, a draft ofSection 10 has always been sent tothe manufacturers for comment,but having a BPMA representativeon the MRC enables the manufac-turers to have more input duringthe development process.
Subcommittees were established towork on revisions to Section six ofthe Manual, which has to do withthe results of non-compliance. Thisis due to be combined into thecurrent Section three, which isentitled Responsibilities: HealthAgency, Water Purveyor, PlumbingOfficial, Consumer, and CertifiedBackflow Prevention Assembly Tester.
All of this will beincorporated intothe “new” sectionfour, Elements of aCross-ConnectionControl Program.
The MRC continues tocollect sample enforce-ment letters along withsample backflow incidentreport forms. These willbe included in SectionEight.
Although there are not ex-pected to be any substantialchanges in the Field Test proce-dures, there are some changes thatare being implemented. One of themost notable of these would be theremoval of the three-psi bufferbetween the relief valve openingpoint and the point at which thefirst check holds on the RP. Thishas always been a confusing issuewith many. The current Manual isnot dogmatic on whether or not thethree-psi buffer is required. It is a“recommended requirement.” Itwas purposely worded this way inorder to give flexibility to waterutilities and other agencies requir-ing field tests to have latitude in
Manual of Cross-Connection Controlcontinued from page one
continued on page six
The newintroductioncombined with thefollowing sectionon hydraulics willmake the Manuala complete sourcefor training courseswhich cover, notonly testing, butgeneral cross-connection controltopics as well.
the high-pressure hose of the gageis moved to the No. 3 test cock andthe sight tube (if needed)is movedto the No. 4 test cock. The No. 1shutoff valve is reopened to repres-surize the assembly. The sighttube is filled and the air is bledfrom the gage. Then the No. 1shutoff valve is closed once again.With the gage at the same level asthe water in the sight tube, the No.4 test cock is opened. At this pointone of three things will happen.The water in the sight tube willremain steady, recede or overflowfrom the sight tube. We are inter-ested in the third scenario, whenthe water in the sight tube over-flows.
Section 9.3.3.2 of the Ninth Editionat T5 states:
If at Test No. 2 step ddddd watercontinues to flow from the No. 4test cock, one of the shutoffvalves is leaking. Observe thereading on the gage, but do notrecord it at this time. Open thebleed-off valve.
If it is not possible to adjust thebleed-off valve to allow a slightdrip at the No. 4 test cock, the
No. 1 shutoff valve should bechecked to make sure it is closedtight. Then proceed to step T8.
Skipping to T8 we find:
If, after checking the tightness ofthe No. 1 shutoff valve, it ispossible to adjust the bleed-offvalve so there is a slight dripfrom the No. 4 test cock, recordthe reading on the gage as thestatic pressure drop across theNo. 2 check valve and return totest No. 2 step fffff. If it is notpossible to adjust the bleed-offvalve so that the water flowingfrom the No. 4 test cock is aslight drip, proceed to step T9.
Moving on to T9:
If it is not possible to adjust thebleed-off valve so that the waterflowing from the No. 4 test cockis a slight drip, and if checkvalve No. 1 was holding lessthan 1.0 psi in Test No. 1, theNo. 1 check valve must berepaired before testing the No. 2check valve. Then, return toTest No. 1 step aaaaa. Otherwise goto step T10.
Finally at step T10:
If check valve No. 1. washolding 1.0 psi or more in TestNo. 1, close the bleed-off valveand open the No. 2 test cock.Record the reading on the gageas the static pressure drop acrossthe No. 2 check valve andreturn to Test No. 2 step fffff.
The important point to note is thatthe tester is not able to completethe test under the above circum-stances if the first check held below1 psi and there was a leaking No. 1shutoff valve. To understand thereasoning behind this requirement,let’s look at what being done instep T10.
Figure 1
Since the No. 1check valve is
holding tight, all ofthe water leaking
throught the No. 1shutoff valve is
dischargeingthrough the No. 2
test cock, and noneof the pressure held
betwen the twocheck valves is
leakng out throughthe No. 2 test cock.
The gage reading isaccurate.
Fou
r
Water is flowing from the sight tubeat the No. 4 test cock. After ob-serving the reading, opening thebleed-off valve arrangement doesnot compensate for a upstreamleak. Then the bleed-off valvearrangement is closed and the No. 2test cock opened. This is done inan attempt to get an accuratereading on the No. 2 check valve,even though water is flowing fromthe sight tube. If the water wasflowing from an upstream shutoffvalve leak, one should have beenable to compensate for it, duringthe test of the No. 1 check valve.So, water must be coming from thedownstream shutoff valve withbackpressure. However, to makesure that no water is flowingthrough the second check valvewhile we take a reading we openthe No. 2 test cock fully. Thisbypasses anywater from aleaking No. 1shutoff valveto atmosphereat the No. 2test cock. Bydoing this,leakage fromboth shutoffvalves will bediverted sothat checkvalve No. 2may be tested.
From Test No.1 we know theNumber one check valve holds atleast 1 psi, the No. 1 check valvemust be closed, since just upstreamof the check valve is open to atmo-spheric pressure. With the No. 4test cock, just downstream of thesecond check valve also open toatmosphere, the reading on thegage (while held at the level of thewater in the sight tube) gives us thedifferential pressure across the No.2 check valve, as shown in Figure1.
If, in the above scenario, the No. 1check valve was not holding thewater trapped between the two-check valves may leak backwardsand out through the open No. 2test cock. Once this pressure leaksaway, the remaining gage readingwill falsely indicate the condition ofthe No. 2 check. This is shown inFigure 2.
From a pure technical sense, the 2nd
check may be evaluated accuratelyproviding the 1st check holds anyvalue above 0.0, even a failingvalue of 0.1 to 0.9 psid. But now,the absolute accuracy of a tester’sgage at the low end of the scalewould be critical. So that theaccuracy of a gage near 0.0 wouldnot impact the field test procedure,the MRC decided to require thatthe cut off point must be 1.0 or
greater. This would provide areasonable safety factor so that thetester would accurately assess thecondition of both check values,even if both shutoff valves leak.
Hopefully, this explanation helpsexplain why it is necessary to stopthe test and repair the No. 1 checkvalve when the No. 1 check valvereading is less than one and there isa leaking No. 1 shutoff valve.
With a leakingNo. 1. shutoffvalve, pressurefrom betweenthe two checkvalves leaksback throughthe No. 2 checkvalve, thusdropping thereading on thegage.
Figure 2
Five
Manual of Cross-Connection Controlcontinued from page threetheir requirements. The three psibuffer does not affect the ability ofthe assembly to prevent backflowbut is there to minimize the nui-sance of water discharging intermit-tently when the line pressurefluctuates. The MRC has dis-cussed this issue much over the lastseveral years. In the Tenth Edi-tion, one can expect to see the“recommended requirement” ofthe three-psi buffer to be dropped.The minimum acceptable value forthe relief opening point will remain2.0 psid and the minimum accept-able value for the first check valvewill be 5.0 psid.
The spill-resistant vacuum breakerwill likely be modified such thatthe order of tests is reversed. Field
experience has demonstrated thatthe check valve reading may beaccurately recorded before the airinlet value. The current NinthEdition SVB procedure was basedmore on the PVB procedure. Theattempt in the Ninth Edition was tomake the SVB and PVB field test
procedures as similar as possible.However, the proposed SVBprocedure will make it easier for thetester.
There was much discussion aboutthe direction of flow test on thesecond check of the RP. Somethought that, the optional testshould be removed from the ap-pendix because of its limitations. Itwas ultimately decided to leave thistest in the appendix of the Manualwith a note highlighting its limita-tions. Although there are limita-tions to this test the MRC wantedthe test to be available to thoseagencies, which require a directionof flow test on the second check ofthe RP.
There are several items that havebeen brought to the MRC forconsideration. Some of these havebeen considered and will be incor-porated into the Tenth Edition.Some items have been rejected andsome are currently under consider-ation. Listed below are some ofthese items.
One of the backflow preventionassembly manufacturers recom-mended that the Tenth Editioninclude the requirement for afollow-up inspection of the facilitiesproducing backflow preventionassemblies in order to renew theapproval of any backflow preven-ters. The staff has had discussionswith some other organizations,which do such audits. This consid-eration is still under review.
A backflow prevention assemblymanufacturer made a presentationat one of the Manual ReviewCommittees recommending theaddition of a new type of backflowpreventer which would be an
Sample incidentforms, and details tohelp the specialist in
cross-connectioncontrol surveys are
coming together forthe Tenth Edition.
Six
integral double check valve assem-bly and water meter. The commit-tee considered this concept andrejected it after discussion.
A backflow prevention assemblymanufacturer recommended theMRC look into some alternatelaboratory tests such as cycle tests,aging tests, adhesion tests, etc.,which could be used in lieu of thefield evaluation. Although some ofthe tests have been discussed toenhance the lab evaluations theMRC believes that the field evalua-tion still necessary. Approximately30% of the backflow preventerspassing the Foundation’s laboratoryevaluation do not pass the fieldevaluation the first time. Thisindicates the field evaluation is stillthe best way to determine the insitu operational characteristics ofthe backflow prevention assembly.
The Manual Review Committeecontinues to discuss and makeprogress on the Tenth Edition ofthe Manual of Cross-ConnectionControl. To make recommenda-tions, or keep up-to-date with thecurrent issues visit the MRC website at http://www.usc.edu/fccchr/mrc/.
Manual of Cross-Connection Control
The spill-resistant vacuumbreaker will likely be modifiedsuch that the order of tests isreversed. Field experience hasdemonstrated that the checkvalve reading may be accuratelyrecorded before the air inletvalue. Se
ven
Training Courses
Tester CourseNow Teaching the SVB!
Los Angeles, CA9-13 July 2001
Incline Village, NV13-17 August 2001
Specialist Course
Los Angeles, CA23-27 July 2001
El Paso, TX17-21 September 2001
Sandusky, OH15-19 October 2001
Foundation for Cross-ConnectionControl and Hydraulic ResearchSchool of Engineering
University of Southern CaliforniaKaprielian Hall 200Los Angeles, California 90089-2531
Upcoming Events
American Backflow Prevention Associa-tion, International Conference•Kansas City, MO
22-25 March 2001
California/Nevada SectionAmerican Water Works AssociationSpring Conference•Garden Grove, CA
23-25 March 2001
American Water Works AssociationAnnual Conference and Exhibition•Washington, DC
17-21 June 2001
American Water Works AssociationDistribution Systems Symposium•San Diego, CA
23-25 September 2001
Tri-State Conference•Laughlin, NV
27-29 September 2001
Western Regional Backflow Conference•Las Vegas, NV
