Improve Water Audits and Minimize Nonrevenue Water
Transcript of Improve Water Audits and Minimize Nonrevenue Water
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Improve Water Audits and Minimize Nonrevenue Water
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Copyright © 2019 by American Water Works Association; [email protected]. All rights
reserved. No part of this publication may be reproduced, stored, or transmitted in any form or by
any means without the prior written permission from the copyright holder.
Prepared for AWWA and M.E. Simpson Co., Inc. by EKB editors John R. Hughes, Kimberly
Retzlaff, Barb Martin, and Dawn Flancher; designers Linda Yeazel and Gillian Wink; and
production manager Diana Aqra.
FRONTCOVER:Waterutilitieshavemadegreatstridesinthelastfewyears
regardingwaterlosscontrol.It’scriticalforutilitiestoreliablyaudittheirsupplies
anddistributionsystemsaswellasassesstheirwaterlossstanding.Awaterauditalso
providesthefoundationaldataautilityneedstoplanacost-effectivestrategytocontrol
excessivelosses.Photographs:M.E.SimpsonCo.,Inc.
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CONTENTS4 FOREWORD5 INTRODUCTION6 WHAT IS A WATER AUDIT?8 USE BEST PRACTICES10 ENSURE ACCURATE WATER AUDITS13 RECOVER UTILITY REVENUE WITH
METER TESTING16 CONSIDER LEAK DETECTION OPTIONS21 DETERMINE WATER LOSS CONTROL
CHALLENGES23 FURTHER READING
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4 ImproveWaterAuditsandMinimizeNonrevenueWater
FOREWORDThisEssentialKnowledgeBriefingdescribeswaterauditsandtheirapplication
asatooltoassessdistributionsystemperformance.Bestpracticesforthedetection
andcontrolofrealandapparentlossesarediscussed,throughensuringmetering
andaccountingaccuracy,aswellasinnovativetechnologiestodetectandcontrol
distributionsystemleakage.Thisinformationprovidesreaderswithessentialtoolsto
addressthiscommonchallengeandprotecttheutility’srevenuestream.
M.E.SimpsonCo.,Inc.,recognizesthechallengethatwaterlosscanposetomany
utilitiesandtheimportanceofeducatingtheindustryonprograms,resources,and
methodsforaddressingwaterloss.That’swhywehavepartneredwiththeAmerican
WaterWorksAssociation(AWWA)tosponsorthedevelopmentofthisEssential
KnowledgeBriefingandprovidethiskeywaterlossinformationtothewater
community.
OurhopeisthatthisEssentialKnowledgeBriefingcanhelptohighlight
theimportantcontributionsofAWWAvolunteersandcommitteesdeveloping
Standards,ManualsofPractice,CommitteeReports,andotherresourcestoadvance
innovationsinthescienceandpracticesofsafewater.Waterauditresourcesoffered
byAWWAprovidesound,consistentdefinitionsforthemajorformsofwater
consumptionandwaterlossencounteredindrinkingwaterutilities.Theyalso
featureasetofperformanceindicatorsthatutilitiescanapplytohelpquantifyand
evaluatetheirwaterlossperformance.Additionalinformationcanbefoundat
www.awwa.org/waterlosscontrol.
We’repleasedtoprovidethisEssentialKnowledgeBriefingelectronicallyat
www.mesimpson.com.ForprintandPDFcopies,pleasecallM.E.Simpsonat
800-255-1521.M.E.Simpsonappreciatesthisopportunitytoshareimportant
informationonthistopic.
MichaelD.Simpson
CEO
M.E.SimpsonCo.,Inc.
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ImproveWaterAuditsandMinimizeNonrevenueWater 5
INTRODUCTIONThroughoutthehistoryofNorthAmerica,abundantwaterresourcescouldbe
readilyandreliablytappedtosupplycommunities.Unfortunately,thatsecurityno
longerexistsinmanyregionsbecauseofachangingclimateandotherenvironmental
stresses,growingandshiftingpopulations,financialconstraints,andevolving
regulatoryprograms.Today’swatermanagersmustensurethey’reaccountableintheir
practicesandhighlyefficientintheiroperations.
Waterlossisacommonchallengefordrinkingwaterutilities,theextentofwhich
variesfromsystemtosystem.Waterauditsareausefultoolthatcanhelpwaterutilities
quantifywaterlossandthefinancialimpactofsuchlossestotheutility,improving
autility’sabilitytoimplementstrategiesforwaterlosscontrol.Arobustwaterloss
controlprogram,includingwateraudits,canbeoneofseveralfactorsthathelpinform
autility’sassetmanagementpracticesand,ultimately,programsforinfrastructure
renewalandreplacementonalargerscale.
Fortunately,reliablemethodsareavailabletohelpwaterutilitiesunderstandand
communicatetheoccurrenceofwaterandrevenuelossesinutilityoperationsandthe
meanstocost-effectivelycontrolthem.ThisEssentialKnowledgeBriefingdescribes
theavailabilityofreliablemethodstoauditthewaterdistributionsystemandutility
revenuestreamaswellasinnovativetechnologiesthatcanbeusedtocontrolleakage
losses,meteringandaccountingerrors,andothercommonsystemlosses.
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6 ImproveWaterAuditsandMinimizeNonrevenueWater
WHAT IS A WATER AUDIT?Waterutilitiescanincurinefficiencies,orlosses,insupply-andcustomer-related
functionsoftheiroperations.Suchlossesincludethephysicalescapeofwaterfromthe
pressurizedpipingsystemasleakage—knownasreal losses.Lossesalsooccurbecauseof
inaccuratemeteringofcustomerconsumption,theftofservice,andtheutility’sown
errantbillingandaccountingpractices—collectivelyknownasapparent losses.The
termnonrevenue waterencompassestherealplusapparentlosses,alongwithunbilled
authorizedconsumptionsuchaswaterusedinmiscellaneousactivitieslikefirefighting.
Inotherwords,nonrevenuewatercomprisesthevolumeutilitieslosefromtheirwater
supplyinfrastructureandtheunbilledvolumesassociatedwithlostrevenuefroma
portionofthesupplythatreachesthecustomer,plustheauthorizedunbilledusage.
TheWaterBalanceDiagramshownonpage7 portraysallcomponentvolumesof
watersupplied,deliveredtocustomers,orlostduringthecourseofareportingyear.The
approachwascreatedbythecombinedeffortsofAWWAandtheInternationalWater
Association.Eachboxrepresentsanannualvolumeofwater,andeachcolumntotals
tothesameamountofwater.Thus,allcolumns“balance”aswatermovesacrossthe
system,andallwaterisaccountedfor.Accordingly,thereisno“unaccounted-forwater,”
atermAWWArecommendsagainstusing.
Instead,AWWArecommendsuseofthetermnonrevenue water,asshowninthe
figure.TheWaterBalanceDiagramprovidesaccountabilityforwaterutilitiesby
definingaclearpathtoquantifythelossvolumesanddemonstratinghowthoselosses
affectutilityoperations.
Waterutilitiesshouldtracktheannualvolumesofwatertheymanage,measuring
theamountofwatersuppliedtotheircustomersandthewaterlost.Thefoundationofa
waterlosscontrolprogramistheannualwateraudit.Auditsarecommonintheworld
offinanceandaccounting.Similarly,autilitywaterauditinvolvesareviewofrecords
anddatathattracestheflowofwaterfromitssource,throughthetreatmentprocess,
intothewaterdistributionsystem,andtocustomerproperties.Thewaterauditusually
existsintheformofaworksheetorspreadsheetthatdetailstheannualvolumesof
watersupplied,customerconsumption,andlossvolumesthatoccurredinacommunity
watersystem.Thestandardwaterauditalsotracksvariouscostsandcalculatesa
varietyofperformanceindicatorstoassessthewaterutility’sefficiency.
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The Water Balance Diagram portrays all component volumes of water supplied, delivered to customers, or lost during the course of a reporting year.
Volume from Own Sources (corrected for known errors)
System Input Volume
Water Exported (corrected for known errors)
Billed Water Exported Revenue Water
Water Supplied
Authorized Consumption
Billed Authorized Consumption
Billed Metered Consumption
Revenue Water
Billed Unmetered Consumption
Unbilled Authorized Consumption
Unbilled Unmetered Consumption
Non- revenue Water
Unbilled Metered Consumption
Water Losses
Apparent Losses
Customer Metering Inaccuracies
Unauthorized Consumption
Systematic Data Handling Errors
Water Imported (corrected for known errors)
Real Losses Leakage on Transmission and Distribution Mains
Leakage and Overflows at Utility’s Storage Tanks
Leakage on Service Connections Up to the Point of Customer Metering
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USE BEST PRACTICESAWWA’swaterauditmethodologyisabestpracticeapproachNorthAmerican
waterutilitiescanusetodevelopconsistentandreliableperformancetrackingand
benchmarkingforandamongwaterutilities.Thismethodologyisembodiedin
AWWA’sManualofWaterSupplyPracticesM36,Water Audits and Loss Control
Programs(availableatwww.awwa.org/store),whichgivesdetailedinstructiononthe
waterauditprocess,bestpracticemethodstocontrolrealandapparentlosses,and
helpfulcasestudiesonthebenefitsofthesepracticesforautility.
Additionally,AWWAprovidesafreespreadsheetsoftwaretool,AWWAFreeWater
AuditSoftware,whichutilitiescanusetoperformastandardizedwateraudit.First
releasedin2006,theExcel-basedtoolhasbeenupgradedseveraltimes,withthecurrent
Version5.0releasedin2014.
Sinceitsrelease,thousandsofwaterutilitiesandindustrypractitionershave
downloadedthesoftwaretocompileawateraudit.Thesoftwareincludesinputsfor
volumesofwatersuppliedbytheutility,waterconsumedbycustomers,andthe
differencebetweenthesetwonumbers,whichamountstowaterlosses.Otherinputs
includedataaboutthewatersystemandthepertinentcosts.Allofthesedataare
usedtocalculateaseriesofperformanceindicatorsthatgiveaneffectiveratingofa
system’sefficiency.Thesoftwarealsoincludesauniquedatagradingcapabilitythat
allowstheusertorate,orgrade,thetrustworthinessofthedatainputintotheaudit.
ADataValidityScorecalculatedbythesoftwarerepresentsthewateraudit’soverall
trustworthiness.
Theauditisonlyasgoodasthedataavailable,anddatavalidationisameansof
verifyingdataaccuracy.In2011,theAWWAWaterLossControlCommitteelaunched
theWaterAuditDataInitiative,whichenlistsdozensofvolunteerwaterutilitiesto
submittheirannualwateraudittobepostedontheAWWAwebsite.Theseauditsmust
firstundergoavalidationprocesstoensurequalitycontrolofthedata.Onlyauditswith
validateddataarepostedonline.ThedatamaybeaccessedontheAWWAWaterLoss
Controlresourcepageatwww.awwa.org/waterlosscontrolandclickingontheValidated
WaterAuditDatalink.
ThestateofGeorgiafollowedthispracticebyimplementingadatavalidation
requirementforitswaterutilities’audits.AllauditsinGeorgiahavebeenvalidated
since2011.ThestateofCaliforniafollowedsuit,andthesubmissionofvalidatedutility
waterauditdataisnowrequired.Duringthepastfewyears,assessmentsofvalidated
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waterauditdatashowedthatsomewaterutilitiesarereportingsubstantialvolumesof
realandapparentlosseswithsignificantcosts.
WiththedevelopmentoftheAWWAmethodologyandimplementationtools,allof
whichcanbeaccessedattheassociation’sWaterLossControlresourcepage,waterutilities
haveavailabletothemalltheyneedtoreliablyaudittheirsupplyanddistributionsystems
andassesstheirwaterlossstanding.Thewaterauditalsoprovidesthefoundationaldataa
waterutilityneedstoplanacost-effectivestrategytocontrolexcessivelosses.
Utilities can use AWWA’s Free Water Audit Software to compile a standardized water audit.
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ENSURE ACCURATE WATER AUDITSWaterresourceshavebeenmonitoredforthousandsofyears.Thefirstfewpagesof
AWWA’sManualofWaterSupplyPracticesM6,Water Meters—Selection, Installation,
Testing and Maintenance(availableatwww.awwa.org/store), arededicatedtotheearly
attemptsatflowmeasurement andthedevelopmentofwatermeters. Today,water
supplymonitoringiscritical.Inthe pastseveralyears,manyUSregionshavefaced
droughtssoseriousthatwateruserestrictions arenowthenorm,andwaterauditing
andtracking accountabilityhavebecomemandatedpractices.
Theabilitytoaccuratelymeasurethewaterconveyedtoawaterutility’sdistribution
systemposesasignificantchallengeformanyutilitiesforvariousreasons,butit’san
importantaspectofawateraudit.Waterauditsbeginwiththetotalamountsthathave
beenpumpedintoadistributionsystem.Thetermwater production isusedtodenotethe
bulkwatervolumes thatconstitutetheoverallwatersupplymanagedbyawaterutility,
includingthe waterauditcomponents.Iftheproductionvolumenumberiswrong,
theauditwillbewrong,too.Everywatersystemthatmeterstheinputofwaterintoits
systemhasthisconcern,regardlessofsystemsize.
Inaddition,manywatersystemsexport,orsell,watertoneighboringwatersystems.
Toreceivefaircompensationforthewatersoldwholesale,connectionpointsmustbe
meteredcorrectly.Thetermexport meters denotesthewatersupplymetersdesignated
forthereceivingwatersystem.Here,too,supplymeteraccuracyisessentialforaproper
wateraudit.
AWWA’sFreeWaterAuditSoftwarecalculatesWaterSuppliedVolumeinthe
ReportingWorksheetasfollows:
Water Supplied Volume = Volume From Own Sources
+ Imported Water Volume – Exported Water Volume
Whatthismeansiswater-suppliedvolumeismadeupofthreecomponents:
waterthathasbeenproducedatawatertreatmentplantbyautilityandputinto
thedistributionsystem,waterautilitymaypurchasewholesalefromasupplier(e.g.,
aneighboringwaterutilityorwatercommission),andanywatersoldwholesaleto
anotherwaterutility.Somewaterutilitiesperformallthreefunctions,whereasothers
mayonlyperformoneortwoofthem.Waterthat’sboughtandsoldwholesaleistermed
custody transfer volume.
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Thewatermetersusedtomonitoreffluentflowatawatertreatmentplantoratthe
custodytransferpointsbetweenwaterutilitiesmeasureflowandrecordthatflow—the
samefunctionsofawatermeterinsideahomeorbusiness.Therefore,themetersneedto
accuratelymeasureflowsandtotaltheflowsoverspecificperiods.
Aflowmetermustbechosencarefullytoensureitcanperformthosetwofunctions
(measuringandrecordingflow)correctly.Also,themeter’ssizemustbematchedtothe
anticipatedvolumeflowingpastthemeter’slocation,andthechosenlocationforflow
measurementmusthavethecorrectlayouttoproperlymeasuretheflow.Finally,the
selectedmetermustallowforperiodictestingandcalibrationtoensureitperforms
withinacceptedaccuracylimitsspecifictoitstype.
It’simperativethatwateroperatorsandmanagersbecomefamiliarwiththe
flowmetertypesusedattheirtreatmentplantsorcustodytransferlocations.Sourcesof
informationforlargerflowmetersincludeAWWA’sManualofWaterSupplyPractices
M33,Flowmeters in Water Supply(availableatwww.awwa.org/store),aswellasthe
previouslymentionedM6manual.
Severaltypesofmetersareusedinwaterproductionandwholesaleapplications.
Thesecanbeclassifiedasdifferentialpressuremeters(Venturimeters,Dalltubes—a
modifiedVenturi—orificeplates,andothers),mechanicalmeters(turbineand
propeller),insertionmeters(Pitottubesandinsertionmagneticmeters),magnetic-style
flow-throughmeters,andultrasonicmeters(strap-onandflow-through).Eachstyle
hascertaincharacteristicsrelatedtouse,accuracy,ranges,andcosts.Whenmeters
arechosenforinstallation,certaintradeoffshavetobeconsidered,asnometerwill
becompletelyaccurateacrossthefullrangeofflowstowhichitmaybesubjected.Asa
result,meterselectionbecomesevenmoreimportant.
Tomeasureflowproperly,ametershouldbesetinalocationwhereconditioned
flowentersthemeter’smeasuringelement.Accuratemeterreadingsdependon
unobstructedflow,andtherequiredlengthsofstraight,unobstructedflowupstream
anddownstreamofthemetersettingvarywithmetertypeandmanufacturer.Ifthis
isn’tconsideredduringmeterselection,metersmaybeinstalledincompromised
settings,causingthemtoperforminaccurately.Moreover,withoutapropersetting
evaluation,autilitymaynotevenknowaboutafaultymetersettingbeforeconducting
itswateraudit.
Asdetailedinthenextsection,waterutilitiesshouldhavetheirproductionmeters
flow-testedregularly,accordingtoapplicableregulatoryrequirements.Intheabsenceof
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anyrulethatstipulatestestingfrequency,itmakesgoodbusinesssensetoperformthe
testingsoitcoincideswiththewaterauditprocess.It’salsoimportanttoconductmeter
calibrationandmaintenanceactivitiesaccordingtothemanufacturer’s
recommendations.Thishelpstoensurewaterutilitieshavereliablenumbers.Howthe
waterauditprocessendswillultimatelydependonhowit’sstarted.That’swhyit’s
criticaltoperformproductionmetertestingandwholesalemetertestingaccuratelyand
regularly.
For water utilities to ensure the accuracy of their water audits, production volumes are the most important quantities to consider. Photograph: AWWA
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RECOVER UTILITY REVENUE WITH METER TESTING
Awatermeterislikeautility’scashregister.Withoutpropermetering,water
utilitiescanlosemoneybecausetheyaren’treceivingfaircompensationforwhatthey
providetotheircustomers.Inaddition,becausemorewaterutilitiesareconducting
wateraudits,apparent losses havegainedprominenceatutilities.Apparentlossesexpress
autility’slossofrevenuebecauseofpotentialmeterinaccuracyaswellasotherissues
suchasaccountingandbillingerrors,unauthorizedwateruse,andimpropermeter
settings(whicheventuallyresultininaccuratemeters).
Equipmentmaintenanceissueshavealong-lastingeffectonautility’soperational
efficiency.Thisisespeciallytrueregardinghowawaterutilityderivesrevenuefromits
dailyuseofequipmentbecauserevenuegenerationistiedtoautility’swatermeters.
Historically,metersmeasuredwaterflowbymechanicalmeansandthushave
beensubjecttowear.Mechanicalwatermeterscaneventuallylosetheabilityto
correctlymeasureandrecordflow.Overtime,waterqualityandhowameterisused
inaparticularsettingcancausemeterstowearout.Water’schemicalmakeupand
hardness,aswellasabrasivematerialsinthewater,canaffectmeterperformance.
Morerecently,electronicmeterswithnomovingpartshavegainedwidespread
acceptanceinthemetermarketplace.Althoughelectronicmetersaren’tsubjecttothe
wearthattraditionalmechanicalmetersmaybesubjecttoovertime,otherpotential
problemscancauseelectronicmeterstomisreadandinaccuratelymeasureflow,
leadingtopotentialapparentlossesfortheutility.Forexample,batteriesmayrundown
oralightningstrikecaninflictdamage.
Otherfactors—suchasthemetersetting,type,andsize—alsoaffectrevenue
generation,sowaterutilitiesneedtoperiodicallytesttheirmeterstoverifytheir
accuracyandmakesurecustomersarebeingchargedfairlysotheutilityreceivesproper
revenueforitsservice.Ameterthatoverregistersflowcanalsobecomeaseriouscause
forconcern.Somerareincidentsofawaterutilityoverchargingcustomershavemade
headlinenews.However,mostofthetime,watermetersdon’toverregister.Instead,they
tendtounderread,resultingincustomerspayingforlesswaterthantheyuse.Thiscan
haveaseriouseffectonautility’srevenue,whicharegularutilitymetermaintenance
programcanhelptoprevent.
Inthecaseofinaccuratemeters,ameter’ssizeisimportant,assmallerandlarger
metersaffectautility’srevenuedifferently.Themeterpopulationofmostwater
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utilitiescommonlyincludesavarietyofmetersizes.Usually,smallerresidentialmeters
areusedingreaternumbersthanlargercommercialandindustrialmeters.However,
asarule,thelargercommercialandindustrialmetersbringinmoreoverallrevenue.
Largemetersmayonlymakeup10–15percentofautility’smeterpopulation,butthey
accountforupto60percentoftherevenuegenerated.Meteraccuracyisacriticalissue
inthesecasesbecausethefailureofafewlargemeterscancauseseriousrevenuelosses.
Determiningwhenit’seasierormorecost-effectivetoreplacemetersinsteadof
repairingthemisanotherfactorinthedecision-makingprocess.Yearsago,mostmeters
wererebuiltbecausethecomponentsweremadeofbrassandcouldberebuilt.Today,a
lotofmetersaremadeofplasticorcompositematerialsanddon’tgetrebuiltiftheyfail
testing.Insomeutilities,thecostofremovingmetersfromtheirsettings,testingand
repairingthem,andreinstallingthemaretoohigh(largecommercialandindustrial
accountsareanotableexception),sonewmetersareinstalledinstead.
Awaterutilityshouldtestitsmetersperiodicallybecausethat’stheonlywayto
knowifameterworkscorrectlyandtherebyprotectutilityrevenues.Howoftena
utilityshouldtestitsmetersvaries,typicallydependingonmetersizeandhowthe
utilityfunctions.Waterratesandthecostofimplementingandmaintainingameter
testingprogramarefactorsthatinfluencetheoperation,frequency,andefficiency
ofametertestingprogram,sothesavingsidentifiedcanhelptobalanceoutthe
implementationcosts.Ifnometertestingprogramisinplace,theutilitysimplywill
notknowwhetherit’sbeingfairlycompensatedforitswater.
Toimplementametertestingprogram,autilityneedstomakeacompleteinventory
ofitsmetersbysizeandtype.Thisinformationisusuallyenteredinaccountingand
billingrecordsandmaybestoredinautility’sassetmanagementsystem.Also,a
utilityshouldreviewpastconsumptionrecordsforeachaccounttolookforadropin
consumptionthatcanindicateamalfunctioningmeter.Becauseutilitiesoftenhave
differenttypesandmodelsofmetersthathavebeenpurchasedovertime,metertesting
andrecordingmustaccountfortheidiosyncrasiesofeachtypeandmodel.
AWWA’sM6manualhasadviceandinstructiononmetertestingandthetwo
essentialmethodsused.Autilitycanremoveameterandbringittoametertesting
facility,orthemetercanbetestedin-place.
Smallresidentialmeterscanbesetuponarandomsamplingtestingprogramso
aselectedpercentageoftheutility’smetersareregularlytested.Thatwaytheutility
hassomeideahowthesmallermetersarefunctioning.Largemetersshouldbetested
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ImproveWaterAuditsandMinimizeNonrevenueWater 15
morefrequentlythansmallermetersbecause,asstated,theyprovidealargerportion
ofrevenuefortheutility.Somestatesalsohaverequirementsfortestingbasedona
meter’ssize.
Thelossofrevenuefromlargemeterscancausemanyproblems.Eachutilityshouldlook
attheexpectedrevenuegeneratedfromitslarge-meteredaccountsandsettest-frequency
parametersbasedontherevenueamount.Theideaistocatchanydropinmeteraccuracy
andrevenuelossearlyandbeforeitbecomesamoresignificantproblem.Tothisend,water
utilitiesshoulddedicateaspecificpercentageoftotalannualrevenuetometertestingand
maintenance.Itmaybeagoodideatoinvolveareawastewaterutilitiesaswell,becausethey
alsoderivetheirrevenuefromwatermeterreadings.Remember,watermetersareautility’s
“cashregisters,”sotheyneedtobeaccurate.
Water meters should be tested to protect customers against inaccuracies that could result in overcharges from overregistration and to protect water utilities from revenue losses resulting from underregistration. Photograph: krungchingpixs/Shutterstock
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16 ImproveWaterAuditsandMinimizeNonrevenueWater
CONSIDER LEAK DETECTION OPTIONSLeakagefromthepipesthatconveyautility’swaterfromsourcetofinalpointof
useisacommonchallenge.Coststowaterutilitiesarehighintermsoflostwaterand
hiddendamagefromleaksthatgoundetectedforalongtime,untilsuddenlyalarge
holeopenstorevealcatastrophicconditionsthatthreatenpublicsafetyandhealth.
Asdiscussedpreviously,suchwaterlossesaretermedreal losses.Accordingto
AWWA’sManualofWaterSupplyPracticesM36,Water Audits and Loss Control
Programs,reallossesare“thephysicallossesoftreatedpressurizedwaterfromthe
distributionsystemduetobreaksandleaksfromthewatermainsandcustomerservice
connectionpipes,joints,andfittings.”
Reallossesequatetothevolumeofwatersuppliedtoadistributionsystemminus
allauthorizeduses(meteredandunmetered),apparentlosses(meteringissues,billing,
andaccountingissues),andestimatesofunauthorizeduses.Reallossesincludeleaks
fromwaterstorage,distributionmains,andserviceconnectionsupthepointof
customermetering.
Waterleakageinadistributionsystemoccursformanyreasons,includingleaks
fromfittingsandappurtenancessuchashydrantsandvalves,seasonalincidentssuch
asfrostheaving,pressureproblemsfromtransientandoperationalissues,poorpipe
materialsandinstallations,corrosiveconditionsinthesoilorbeddinginwhichapipe
islaid,andmore.Lossvolumewillvarydependingoneachsystem’scharacteristicsand
operationalprocedures.Losscontrolalsovariesfromsystemtosystem.Theabilityto
controltheselossesdependsonseveralvariables,someofwhichutilitiescancontroland
others,liketheweather,theycan’t.
Thevolumeofannualleakagelossesinadistributionsystemdependsonthe
numberofleaksoccurring,theirmagnitude,operatingpressure,and—perhapsmost
important—thetotaltimetheleaksgounaddressed.Smallleaksthatrunforalong
timewithoutbeingdetectedcanactuallypassmorewaterthanlargeleaksthatrunfor
ashorttime.Smallleakscanrunforyearswithoutbeingdetected,becausethewater
willfindapathofleastresistanceandrununtilavoidisfilledorapathiscarvedout.
Mostleakseventuallysurfacethroughcracksinthegroundorstreetpavement,atthe
wastewatertreatmentplant,oratacreekorriver.
Leakawarenesstimecanhaveasignificantinfluenceonhowquicklyaleakis
repairedandtheresultingwaterlossvolume.Typically,mainbreakshaveashort
awarenesstimebecausetheysurfacequicklyandarelocatedandrepairedquickly.
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ImproveWaterAuditsandMinimizeNonrevenueWater 17
Smallerleaksaremorelikelytohavelongerawarenesstimesbecausetheydon’tget
discoveredunlessthey’vesurfacedorareidentifiedthroughaleakdetectionprogram;
however,oncediscoveredandlocated,theyusuallygetrepairedquickly.Leaksonthe
customersideofaservicecanhavealongerawarenesstime,andoncediscoveredand
located,mayhavealongrepairtimebecausethecustomertypicallyhastotakecareof
therepair.
Therearemanytypesofleakdetectiontechnologiesavailabletohelpshortenleak
awarenesstimeandminimizeautility’sreallosses.Twogeneralcategoriesareacoustic
andnonacousticleakdetection.
Acousticleakdetectionisprobablythemostcommonandeasiestformofleak
detectionusedtoday.Waterleakingfromapipethat’sunderpressurecreatesasound
waveofenergythattravelsalongthepipewallsandwatercolumn.Iftheleakislarge,
partofthesoundwavewillbetransmittedtothesurroundingsoilor,insomecases,the
hardpavementofastreetorsidewalk.
Asthesoundwavetravelsalongthepipewallandwatercolumn,itlosesenergy
asthewaveencounterspipejointsandotherfittings.Rectilinear propagationisaterm
thatmeanswavestravelinstraightlinesorapath.That’swhatasoundwave(energy)
fromleakagedoes:ittravelsinastraightline.Whenthesoundwaveencountersatee,
four-waycross,orserviceconnection,partofthewavesplitsoffandtravelsuptheline
whiletherestofthewavecontinuestravelingalongthepipe-wallpathorwatercolumn.
Elbowscanalsohaveaneffectonhowsoundwavestravel.Ateachpointwherethe
soundwaveis“forced”tochangedirection,itlosesenergy,andthewavecanbecome
slightlydistorted.
Theabilitytouseacousticdetectiondependsonseveralvariablesthateveryutility
needstoconsidertoeffectivelypinpointleaks,includingpressure,pipematerials,soil
types,watertable,groundcover,andpipesize.Arangeofacoustictechnologiesare
availablefordifferentapplications.
Hydrophones.Hydrophones,thesensorsusedfordetectingsoundwavesina
watercolumn,don’tdependonpipematerialorpipesizeforthesoundwavestobe
sensed.However,thehydrophonesmustbeinfullcontactwiththewatercolumn.This
isusuallyaccomplishedby“charging”firehydrantsandinstallingthehydrophones
atthehydrants.Thehydrantcan’tleakorthesoundoftheleakyhydrantwillbe
pickedup.
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18 ImproveWaterAuditsandMinimizeNonrevenueWater
Transducers.Becausetheyenablebettersensitivityindetectingnoise,electrical-
mechanicaltransducersweredevelopedtoconvertmechanicalsoundwavestoelectrical
signalsthatamplifyandtransmittoearphonestohelpthelistenerhearsounds.
Moderntransducersusedforleakdetectionareextremelysensitiveandcanpickup
noisethat’sfaintandfaraway.
Leak Correlators.Createdinthe1970s,leakcorrelatorsusetwotransducer
microphonesplacedincontactwiththewaterpipe,valve,hydrant,orservice
connectionatthepointatwhichtheleaknoisewasheard.Whencorrelatorswerefirst
developed,thisareawouldbebracketed,withonetransducermicrophonemountedon
eachsideofthesuspectedleakarea.Thecorrelatorwouldreceivetheelectronicsignal
fromeachtransducerbyhardwireorradioandcomparethetime-delaydifferencefor
theleaksoundwavetoarriveateachsensor,andthenitwouldcalculatethepositionof
theleakbasedonthetimedelay.Leak-detectioncorrelatortechnologyhasimproved
greatlysinceitsintroductionandisoneofthemaintoolsforleakpinpointingbyleak-
detectionspecialists.
Leak Loggers.Transducertechnologyforleakdetectionhasbeenincorporated
intowhat’snowknownasleakloggers.Thetransducerisconnectedtoarecorderthat
canbeprogrammedtoturnonandoffatdifferenttimestolistentopipes.Therecorded
soundscanbedownloadedandfurtheranalyzedforthepresenceofaleak.Someloggers
canbeleftinplaceforlongperiodsandsendaradiosignaltoareceiver,similarto
automatedwatermeterreads,allowingforlongerperiodsofleak-noiselistening.
Severalnonacousticleakdetectionapproachesalsohavebeendeveloped,eachwith
advantagesanddisadvantages.Suchtechniquescurrentlyareusedcommerciallyto
varyingdegrees.
Tracer Gas Method.Forsmallleaksthatcan’tbedetectedorpinpointedby
traditionalacousticmethods,tracergasleakdetectionmaybeeffective.Thetracergas
methodusesoneoftwopotentialgases:hydrogenorhelium.Gasisinjectedintothe
pressurizedpipelinethroughstandardpipefittings(taporfirehydrant),andthegas
travelswiththeflowofthewaterinpressuredpipelines,ortowardaventedoutleton
dewateredpipelines.Astheliquidexitstheleak,itreturnstoagaseousform.While
walkingdirectlyoverthetestsectionofpipe,theoperatorusesaspecializedinstrument
thatcontinuouslysensestheatmosphereatgrade.Whengasisdetectedatthesurface,
theinstrument’svariablesensitivitysettingcanquicklyverifyandpinpointthe
leak’slocation.
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ImproveWaterAuditsandMinimizeNonrevenueWater 19
Infrared Imaging.Infraredimagingwasdevelopedinthe1950sandimproved
inthe1960stoproducelineimages.Infraredallowsuserstoidentifytemperature
differences.Theadventofdigitaltechnologyhasmadeitpossibletocreateisothermic
images.Waterleakscanbeidentifiedbycalculatingtemperaturedifferences.This
techniquebecameusefulforleakdetectionassociatedwithbuildinginspections.
Camera Inspection.Camerainspectionhasbeenusedforleakdetectionalmost
aslongasclosed-circuitTVhasexisted.Today’sfiberoptictechnologymakesitpossible
togetinsidewaterpipestolookforleaks.Camerainspection,combinedwithtrenchless
technology,allowsforrepairstobemadetoleakypipesinextremelydifficultlocations
withoutdigging.
Ground-Penetrating Radar.Usingradarpulses,ground-penetratingradar(GPR)
createssubsurfaceimages.Whentheradarsenseswater,aprofileisproducedthatmaps
thelocation.GPRhasbeenaroundsincethe1970s.Utilitieshaveusedittomappipes
andutilitylinesundercitystreetsaswellastodetectleaks.
Microwave Remote Sensing.Anewformofleakdetectiononthemarketis
theuseofmicrowaveremotesensingviasatelliteimagery.Satelliteimagesofan
areaareanalyzedtoidentifyspotsthathaveapotentialforleakage.Afterareasare
narroweddown,aleakdetectionteamcanbesenttoaspecificlocationtosearchfora
suspectedleakandpinpointit.Thismethodcanshortenthesurveyingtimeforlarger
watersystems.
Intheend,leakageremainsacommonchallengeforwaterutilities.Byusingthe
AWWAFreeWaterAuditSoftware,utilitiescancalculatetheirreal-lossamountsso
arealisticleakdetectionprogramcanbedeveloped.Suchaprogramcanhelpautility
optimizeitsreturnoninvestment.Privateleakdetectionfirmscanprovidethistype
ofserviceforsmallerutilities.Largerwatersystemsoftenwillhavetheirownleak
detectionteamsthatcanbesenttoreactivesituationsandcanconductproactive
surveys.Tolearnmoreaboutleakdetection,waterlosscontrol,andappropriateoptions
foryourutility,readAWWAManualM36,Water Audits and Loss Control Programs.
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20 ImproveWaterAuditsandMinimizeNonrevenueWater
.
Acoustic devices allow users to detect the presence of leak noise and accurately pinpoint leak locations quickly. Photograph: M.E. Simpson
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ImproveWaterAuditsandMinimizeNonrevenueWater 21
DETERMINE WATER LOSS CONTROL CHALLENGES
Althougheachwaterutilityhasuniquecharacteristics,somewaterloss
characteristicsarecommontoallsystems;othersaffectsystemsofspecificsizes.
It’simpossibletoconsidereverycombinationofissues,butit’sworthcomparing
thewaterlosschallengesofsmallerwatersystemswiththoseofmedium-sizedand
largersystems.
Anyoneinterestedindevelopingawaterlosscontrolprogramshouldbeginwith
theWaterBalanceDiagramshownonpage7.Theapproachprovidesthebasisfor
understandinghowutilitiesareabletotrackwaterlossandconsidershowwatergets
intoawatersystem,isconsumed,andwhereitcanbe“lost,”ornotconsumedbutstill
accountedforortracked.However,dependingonawaterutility’ssize,thereareissuesto
considerregardinghowutilitiestrackwateruses.
Todeterminewatersuppliedforautility,largeorsmall,waterflowneedstobe
measuredcorrectly.Thewatervolumesuppliedcomprisesthreecomponents:water
thathasbeenproducedatawatertreatmentplantandputintothedistribution
system,waterautilitymaypurchasewholesalefromasupplier,andanywatersold
wholesaletoanotherwaterutility.Somewaterutilitiesperformallthreefunctions;
othersperformoneortwoofthefunctions.Thekeyhereistoensureeachpointof
finalproduction,wholesalepurchase,orresaletoanotherwholesalecustomeris
meteredcorrectly.
Smallwatersystemscanhaveaslittleasonewelloronesmallsurfacewater
treatmentplant.Somesmallsystemspurchasewaterwholesalefromasupplier.Insuch
cases,it’sgenerallyeasyforautilitytodeterminecorrectwater-productionvolumes;
however,watermetersshouldbetestedregularlytoverifytheiraccuracy.Themeter
atthewellortreatmentplantmaynotbeinagoodsettinginsomesmallsystems,so
testingformeteraccuracyiscriticaltoverifyamountsproduced.
Medium-sizedwaterutilitiestypicallyhavemorestaff,resources,andwatersources.
However,themoresourcemeters,thebiggerthepotentialforsourcemeterissues.The
accountingbecomesabitmorecomplicatedwithanincreasingnumberofmetersand
oftenmorecomplexratestructures,butmeteraccuracystillneedstoberegularly
verified.Inaddition,watervolumesforeachmeterneedtobeweightedtogetanoverall
accuracynumberfortotalannualinput.
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22 ImproveWaterAuditsandMinimizeNonrevenueWater
Largerwatersystemshavemorecomplexproductionsystems.Citiescanhavelarge
waterproductionmeterslocatedinoldertreatmentplantsettingsthatcanbemore
challengingtotestandverifytoensureproperwaterflowmeasurement,causing
difficultyinaccuratelyconfirmingwaterproductionvolumes.Also,manylarger
systemsexportwatertosmallersystems.Somelargersystemsmayhaveseveral
wholesalecustomersandwatercommissionsthattransportwateroverlongdistances.
Asaresult,determininganannualtotalwatersysteminputcanbeabigjob!Thisisone
ofthebiggestchallengesforlargerwaterutilities.
WiththedevelopmentoftheAWWAmethodologyandimplementationtools,
waterutilitieshavetheresourcestheyneedtoreliablyaudittheirsuppliesand
distributionsystemsandassesstheirwaterlossstanding.Awaterauditalsoprovides
thefoundationaldataautilityneedstoplanacost-effectivestrategytocontrol
excessivelossesandhelpinformbroaderdecisionsrelatedtoassetmanagementand
infrastructurereplacement.
Historically,themotivationforawaterutilitytocompileanannual
waterauditwasvoluntary.However,since2005,severalstateshaveenacted
requirementsforannualwateraudits,andthenumberofwaterutilitiesroutinely
compilingwaterauditsisgrowing.Theimportantstepistogetstarted—then
buildontheresults.
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ImproveWaterAuditsandMinimizeNonrevenueWater 23
FURTHER READINGAWWA,2018(3rded.).ManualofWaterSupplyPractices,M33.Flowmeters in
Water Supply.AWWA,Denver.
AWWA,2016(4thed.).ManualofWaterSupplyPractices,M36.Water Audits and
Loss Control Programs. AWWA,Denver.
AWWA,2016.The State of Water Loss Control in Drinking Water Utilities,white
paper.AWWA,Denver.
AWWA,2012(5thed.).ManualofWaterSupplyPractices,M6.Water Meters—
Selection, Installation, Testing, and Maintenance. AWWA,Denver.
VanArsdel,J.,2017.AccurateWaterAuditsRequireAccurateMasterMeter
CalibrationandTesting.Opflow,43:2:10.https://doi.org/10.5991/OPF.2017.43.0008.
VanArsdel,J.H.,2017.ConsiderYourLeakDetectionOptions.Opflow,43:4:10.
https://doi.org/10.5991/OPF.2017.43.0021.
VanArsdel,J.H.,2017.MeterTestingandMaintenanceProtectWaterUtility
Revenues.Opflow,43:3:16.https://doi.org/10.5991/OPF.2017.43.0016.
VanArsdel,J.H.,2017.SystemSizeCanDetermineWaterLossControl
Challenges.Opflow,43:5:16.https://doi.org/10.5991/OPF.2017.43.0029.
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