shower-based water savings flow rate vs. duration vs. volume · customize their shower...

Shower-BasedWaterSavings

FlowRatevs.Durationvs.Volume

AnIndependentMaPResearchReport

January2017

AuthorsBillGauley,P.Eng.,Principal,GauleyAssociatesLtd.JohnKoeller,P.E.,Principal,Koeller&Company

TABLEOFCONTENTS

1.0 Introduction..................................................................................................................................1

2.0 AverageShowerheadFlowRates–REUS1999vs.REUS2016......................................4

3.0 ShowerFlowRatevs.Durationvs.Volume........................................................................5

4.0 SummaryandConclusion.........................................................................................................9

FIGURES

Figure1-AverageDailyIndoorPerCapitaWaterUseREUS1999andREUS2016

Figure2–1999REUSvs.2016REUSPercentageFlowRates

Figure3–ShowerFlowRatevs.Durationvs.Volume,1999REUSvs.2016REUS

Figure4–AverageDailyIndoorPerCapitaWaterUsewith95%ConfidenceErrorBars

January2017 Gauley/Koeller:www.map-testing.com

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HOWSHOWERHEADFLOWRATESIMPACTSHOWERDURATIONANDVOLUME

1.0 Introduction

TwoofthemostimportantresidentialwaterdemandstudiesinNorthAmericaarethe1999and

2016ResidentialEndUsesofWaterStudies(REUS1999andREUS2016)completedbyAquacraft,

Inc.1Thesetwostudiesdataloggedwateruseinalargenumberofsingle-familyhomes2across

theUSAandCanada toquantify thevolumeassociatedwitheach individualwaterusewithin

thehome.

The1999report3identifiedanaverageindoorwaterdemandof69.3gallonspercapitaperday

(gpd).By2016,thisdemandhadfallento58.6gcd–adeclineofabout10.7gcdover16years

oranaverageofabout1%peryear4.Whatseemsremarkableisthatafull90%ofthisreduction

wasattributedtoonlytwohouseholdusecategories-toiletdemandsdeclinedby4.3gcdand

clotheswasherdemandsdeclinedby5.4gcd(seeFigure1reproducedfrom2016REUS).

Sowhysolittlesavingsassociatedwithshowers?

The 2016 REUS determined that showering currently accounts for about 19% of indoor

residentialwaterdemands;thatpeopletakeanaverageof0.69showersperday;andthatthe

average shower duration is about 7.8 minutes long. Of course, many people shower more

frequently andmany less frequently, andmany take longer showers andmany take shorter

showers–but,onaverage,wetakeabout0.69showersperdaywithadurationofabout7.8

minutespershower.

1WhileREUSreportswerepublishedin1999and2016,waterdemanddatawerecollectedintheyearsprecedingpublication.21,187homeswereloggedin1999and762homeswereloggedin2016.3WaterResearchFoundation’s1999ResidentialEndUsesofWater(Mayeretal.1999),http://www.waterrf.org/PublicReportLibrary/RFR90781_1999_241A.pdf4WaterResearchFoundation’s2016ResidentialEndUsesofWaterStudyUpdate–Version2(Mayeretal.2016),http://www.waterrf.org/Pages/Projects.aspx?PID=4309)


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Whileshoweringaccountsforalmostone-fifthof indoorresidentialwaterdemands,thereare

challengesassociatedwithreducingshower-basedwaterdemandsthatdonotexist fortoilet-

based and clothes washer-based demands – namely, the personal and tactile experience

associatedwithshowering,i.e.,end-userbehavior.Althoughtheprimaryreasonforshowering

may be to “get clean”, many people enjoy the experience of showering – the warmth, the

comfort, the feelof thewater striking theskin. Showering isaverypersonalexperienceand

product manufacturers have responded by designing many hundreds of different models of

showerheads,eachwithslightlydifferentspraycharacteristics. Someshowerheadsarehand-

held,while somearewall-mounted; someareveryhigh-flow,while someare superefficient;

some provide high-velocity sprays, while some feel like a gentle rain shower; some offer a

numberofdifferentspraypatterns,whilesomearestrictlyutilitarian,etc.Inshort,peoplecan

customize their shower ‘experience’ almost anyway they choose. However, because of the

significant impact of personal preference on showerhead selection, in an unfettered

marketplaceitislikelythatmanypeoplewouldchoosetoinstallhighflowrateshowerheads–

sacrificingwaterandenergyefficiencyforcomfort. What’smore,showerheadstendtobefar

less expensive than clothes washers or toilets, and much easier to change-out. That is,

homeownersthatarenot fullysatisfiedwiththeir“showerexperience”(forwhateverreason)

caneasilyreplacetheiroffendingfixtureforamoreacceptableone.

This ‘easeof installation’ is thecruxof thechallenge facedbywaterutilitiesandshowerhead

manufacturerstryingtoreducecustomerwaterdemandsandachieveproductefficiency.For

example,while it is relatively inexpensive forautility togiveawayor rebate thepurchaseof

efficientshowerheadsbytheircustomers,anditisrelativelyeasyforahomeownertoinstallan

efficient showerhead (usually without the need to hire a plumber), it is just as easy for a

homeowner to remove thenew showerhead if they are not happywith its performance and

replace it with a potentially high-flow-ratemodel, eliminating any expectedwater or energy

savings. Perhaps this iswhy a quickweb search indicates there are far fewerwater utilities

rebatingorgivingawayefficientshowerheadsnowthantherewasadecadeago.


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As illustratedabove,between1999and2016,shower-basedwaterdemandsdeclinedbyonly

0.5gcd!Thereseemstobetwosimplepossibilitiesforthislowlevelofsavings-either:

a) showerheadtechnology(andefficiency)didnotimprovesignificantlybetween1999and

2016,OR

b) asshowerheadsbecamemoreefficient(i.e.,withlowerflowrates),peoplecompensated

by taking longer showers, thus negating the potential water savings associated with

thoselowerflowrates.

Butthereisalsoathirdpossibility–thatactualshowerheadsavingsaregreaterthanthat

indicatedinFigure1,andthispossibilityisdiscussedinSection4.

Figure1


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2.0 AverageShowerheadFlowRates–REUS1999vs.REUS2016

AcomprehensiveanalysiswascompletedbyGauley/Koelleronshower-baseddatacollectedas

part of the1999 and2016Residential EndUse Studies.5 The analysis first looked at average

showerheadflowrates6. Onlyflowratesbetween1.0and4.0gallonsperminute(gpm)were

considered intheanalysisasapproximately97%oftheshower-basedevents identifiedbythe

TraceWizard programusedbyAquacraft, Inc. fellwithin this flow rate range7and therewas

someuncertainty if all eventswith veryhighor very low flow rateswere truly shower-based

events.

TheGauley/Koelleranalysisgroupedtheapproximately42,500showereventsrecorded inthe

REUS1999 and the approximately 15,500 shower events recorded in the REUS2016 into

incrementsof0.2 gallonsperminute (gpm),basedon their average flow rate. From this, the

percentage of shower events that occurred in each flow rate increment for each of the two

studies(Figure2)wascalculated.

The analysis clearly shows a trend towards lower flow rate showerheads between 1999 and

2016. Forexample,the1999dataidentifiedthatonly44%of installedshowerheadshadflow

ratesof2.0gpm(themaximumflowrateforaWaterSense®labeledshowerhead)orlesswhile

by2016thisratehadincreasedto56%. Notethat ifonlyshowerheadswithflowratesof2.0

gpmorlessareconsidered“efficient”,then(atleastasof2016)approximately44%ofinstalled

showerheadscontinuetooperateinefficiently.

Theresultsofthisanalysis indicatethatshowerheadtechnology(at least insofarasflowrates

areconcerned)hasimprovedbetween1999and2016.SowhydidtheREUstudiesidentifyso

5Shower-baseddatafromtheResidentialEndUsesofWaterstudieswereprovidedbyCo-PrincipalInvestigator,PeterMayer,P.E.6TheREUSstudiesrecordedactualflowrates,notratedflowrates.7Waterdemanddatacollectedaspartofthe1999and2016REUSareanalyzedusingtheTraceWizardsoftwareprogram.Thisprogramusestheflowrateandflowdurationofeachrecordedwateruseeventtoassigntheeventtotheappropriatehouseholdfixtureorappliance.WhiletheaccuracyoftheTraceWizardanalysisisconsideredveryhigh,itisnotconsideredperfect.ForafulldescriptionoftheTraceWizardprogrampleaseseehttp://www.aquacraft.com/downloads/trace-wizard-description/


5

littleshower-basedwatersavingsbetween1999and2016?Thelowlevelofsavingscouldbe

explainedifpeopledo,onaverage,compensateforlowerflowratesbytakinglongerduration

showers.Butisthisreallythecase?

3.0 ShowerFlowRatevs.Durationvs.Volume

Theprimarypurposeofthisstudywastoverify ifthere isatendencyforshowerdurationsto

increaseasflowratesdecrease,possiblyresulting in littleornowatersavingsassociatedwith

the use of lower flow rate showerheads. An analysiswas completed on the 1999 and 2016

REUSdatatodeterminetherelationshipbetweenshowerflowrateandduration(notethatflow

ratemultipliedbydurationequalsshowervolume).

Figure2


6

Forreasonsstatedearlier,onlyflowratesbetween1.0and4.0gallonsperminute(gpm)were

included in the analysis8. For similar reasons, only shower durations between 2.0 and 20.0

minuteswereincludedintheanalysis9.

WhilewaterdemanddataforthetwoREUstudieswerecollectedmorethan15yearsapartand

there was some variation in the participating communities, the results of the flow rate vs.

durationanalysisprovedtoberemarkablysimilarforthetwodatasets.Forexample,Figure3

illustrates the relationshipbetweenshower flowratevs. showerdurationvs. showervolume.

Note that showerduration increasesonlyminimallyas flowratesdecrease forboth the1999

and2016datasets,at leastforflowratesbetween1.0and4.0gallonsperminute. Forevery

8Whilesomepeoplemaypurposelychoosetoinstallverylowflowrateshowerheads,itisprobablethatthelowflowratesrecordedinsomeoftheparticipatinghomesweretheresultoflowwaterpressuresand/orexcessivemineralbuildupinthewatersupplypipingorshowerhead,ratherthanasaconsequenceofshowerheaddesign.9Thisrangeincluded96%ofallshowereventsandexcludedeventsthatmayhavebeenmisidentifiedasshowersbytheTraceWizardsoftware,e.g.,eventswithdurationsaslowas10secondsorashighas173minutes.

Figure3


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0.2gallonperminutedecrease in flowrate, theaverageshowerduration increasesbyonly8

secondsbasedon1999dataandbyonly2secondsbasedon2016data.Bothsetsofdataalso

showadecreaseinshowervolumeastheflowratedecreases.Forevery0.2gallonperminute

decreaseinflowrate,theaverageshowervolumedecreasesby1.24gallonsbasedon1999data

andby1.44gallonsbasedonthe2016data.

Figure3clearlyillustratesthat,onaverage:

• people do not compensate for lower flow rates by commensurately increasing the

durationoftheirshower,and

• lowerflowrateshowerheadsdoresultinaloweroverallshowervolume.

While some people take longer showers and some take shorter showers, the data shows, in

general,people tend to follow theirownunique routine for showering regardlessof the flow

rateof the showerhead. In fact, it ispossible that the fewextra seconds spent showeringat

lowerflowratesmaybeprimarilyrelatedtowashingandrinsinghair.

Sowhyweretheshower-basedsavingsidentifiedinthe2016REUSsolow?Partoftheanswer

maybe inhowthe resultsarepresented. While, for simplicity sake, tables in the2016REUS

report identifyaveragepercapitapershowerwaterdemandsof11.6gallons for1999andof

11.1 gallons for 2016, these values, by themselves, do not articulate the margin of error

associatedwith their calculation. Figure4 (reproduced fromFigure6.13 inREUS2016) shows

theaveragedailypercapitademandsforeachindooruseaswellasthemarginoferroratthe

95%confidencelevel.Assuch,whileaverageshower-baseddemandsin1999areidentifiedas

11.6gcd,thevalue(atthe95%confidencelevel)couldactuallyrangefromaslittleasabout11.2

gcdtoashighas12.0gcd,while2016shower-baseddemandscouldrangefromabout10.5to

11.7gcd.Basedonthisanalysis,averagedailyper-showerdemandscouldactuallybeasmuch

as0.5gallonshigherin2016orasmuchas1.5gallonslowerin2016.


8

Figure4


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4.0 SummaryandConclusion

Theflowrateanalysis(resultsillustratedinFigure2)identifiedahigherpercentageofinstalled

lowflowrateshowerheadsin2016thanin1999.

The flow ratevs.durationanalysis indicated thatpeople tend toonlymarginally increase the

durationoftheirshowertocompensateforlowerflowrates.

Basedonapplyinga95%confidenceintervaltopercapitashower-baseddemands,itispossible

that the average 0.5 gallons per capita per day shower savings between 1999 and 2016 (as

identifiedinthe2016REUSreport),maybesomewhatunder-reportedandmayactuallybeas

highas1.5gallonspercapitaperday.

While studies have shown that people tend to prefer higher flow rate showerheads10, the

resultsofthisanalysisclearlyshowthatwatersavingscanbeachievedbyusinglowerflowrate

showerheads. As such, it appears that low flow rate showerheads that meet customers’

expectationforperformancewillprovidethebestopportunitytomaximizewatersavings.

Waterutilities interested inachievinghigher levelsofwater savings shouldbeencouraged to

consider(orre-consider)promotingorrebatinghigh-performancelowflowrateshowerheads.

Pleasesendanyquestionsyoumayhaveregardingthecontentofthisreporttotheauthors:

BillGauley,P.Eng.,Principal,GauleyAssociatesLtd.,[email protected]

JohnKoeller,P.E.,Principal,Koeller&Company,[email protected]

NOTE:TheauthorswouldliketothanktheWaterResearchFoundationfortheirsupportof

theResidentialEndUsesofWaterstudiesandPeterMayer,P.E.,Principal,WaterDM,forhis

consultationandpeerreviewofthiswork.10High-EfficiencyShowerheadPerformanceStudy,2009,Gauley,Robinson,Elton.Reportcanbefoundat:http://www.map-testing.com/assets/files/Veritec-Waterloo%20Final%20Report%20Dec%202009%20copy.pdf

TABLEOFCONTENTS

1.0 Introduction..................................................................................................................................1

2.0 AverageShowerheadFlowRates–REUS1999vs.REUS2016......................................4

3.0 ShowerFlowRatevs.Durationvs.Volume........................................................................5

4.0 SummaryandConclusion.........................................................................................................9

FIGURES

Figure1-AverageDailyIndoorPerCapitaWaterUseREUS1999andREUS2016

Figure2–1999REUSvs.2016REUSPercentageFlowRates

Figure3–ShowerFlowRatevs.Durationvs.Volume,1999REUSvs.2016REUS

Figure4–AverageDailyIndoorPerCapitaWaterUsewith95%ConfidenceErrorBars

shower-based water savings flow rate vs. duration vs. volume · customize their shower...

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