Improve Water Audits and Minimize Nonrevenue Water

2 ImproveWaterAuditsandMinimizeNonrevenueWater

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.

ImproveWaterAuditsandMinimizeNonrevenueWater 3

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


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.


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.


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.


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


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


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.


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.


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


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


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


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


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


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.


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.


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.


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.


.

Acoustic devices allow users to detect the presence of leak noise and accurately pinpoint leak locations quickly. Photograph: M.E. Simpson


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.


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.


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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