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PVC VS HDPE PRESSURE PIPE FOR WATER MAINS

In North America today, new installations of drinking-water distribution systems are primarily PVC pipe.<br>More than one million miles of PVC pressure pipe are currently in service, including hundreds of millions<br>of gasketed joints and tens of millions of taps.

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PVC VS HDPE PRESSURE PIPE FOR WATER MAINS

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  1. PVCVSHDPEPRESSUREPIPEFORWATERMAINS • ACOMPARISONBASEDONSIXTYYEARSOFWATERWORKSEXPERIENCE • InNorthAmericatoday,newinstallationsofdrinking-waterdistributionsystemsareprimarilyPVCpipe. MorethanonemillionmilesofPVCpressurepipearecurrentlyinservice,includinghundredsofmillions ofgasketedjointsandtensofmillionsoftaps.PVCpipehasnowbeeninserviceformorethansixtyyears andisusedinover40,000municipalities.PVCusersareenjoyingthebenefitsofaneasy-to-install,long- life,maintenance-freeproductwhichmeetsallNorthAmericanhealthandsafetyregulations. • Inaddition,thelongevityandsustainabilityofPVCpipeareunsurpassed: • PVCpipe’slifeexpectancyis100+years(AWWARF/UtahStateUniversitystudies). • PVCpipe’slongliferesultsinfavorablelife-cyclecosts. • PVCpipesprovidealargerflowarea,therebyreducingpumpingcosts. • PVCpipesarenotsubjecttooxidationoftheinsidesurfacecausedbychemicalsusedforbothinitialwater • maindisinfectionandin-servicedisinfection. • DrawbackstotheUseofHDPEPressurePipe • The first ASTM standards for PVC and HDPE pressure pipe were written in the early 1960s. During the intervening fiftyyears,PVCwaterpipehasseenaperiodofsustainedgrowth,whileHDPEwaterpipehasbeenprimarilylimited totrenchlessapplications.SomeofthemajordrawbackswithHDPE’suseforwatermainsare: • The lower strength of HDPE compared to PVC requires HDPE to have pipe walls that are 2½ times as thickinordertoprovideequivalentpipestrengthandsafetyfactor.Thisaddssignificantlytotheresources consumedandthecostofthepipeandappurtenances. • HDPEpipedoesnothaveabell-and-spigotjointoption.Thisrepresentsadisadvantageforopen-cut • installationandforsystemmaintenance. • The thicker walls of HDPE result in reduced flow area. The higher velocities needed to provide the same gpmresultinincreasedfrictionlossandadditionalpumpingcosts.Alternatively,HDPEpipeswouldneed tobeup-sizedtomatchtheinsidediameterofPVCpipe. • HDPEpipesmaybesusceptibletooxidativedegradationwhenexposedtocommonwaterdisinfectants. • HDPEpipesaresusceptibletopermeationincontaminatedsoils,evenwhencontaminantconcentrations arelow(AWWARFstudy“ImpactofHydrocarbonsonPE/PVCPipeandGaskets”) • Summary:thecostsforapolyethylenewaterpipelinearehigherthroughoutitslife. • HDPEDecreasesSafetyFactor • The HDPE industry has reduced the safety factor for its new PE4710 pipe products. The traditional safety factorof • hasbeenreducedto1.6inHDPEASTMandAWWAstandards.Asimplecalculationprovesthepoint: • Foranystructure,theSafetyFactor=MaterialStrength/DesignStress • FornewandoldHDPEmaterials,theMaterialStrength(called“HDB”)=1600psi • FortheoldHDPEmaterials,DesignStress=800psi oSafetyFactor=1600psi/800psi=2.0 • ForthenewPE4710material,DesignStress=1000psi oSafetyFactor=1600psi/1000psi=1.6 • This concept is very simple. If two materials have the same strength, the only way to increase the design stress is to decrease the safety factor. This practice represents increased risks and shorter life-expectancy for any material, but especially for a new and unproven material in a 100-year life application. On the reverse side of this page is informationaboutthedifferencesbetweenPVCandHDPEmaterialsusedforpressurepipe. Uni-Bell PVC Pipe Association | 2711 LBJ Freeway, Suite 1000 | Dallas, TX 75234 Phone: (972) 243-3902 | Fax: (972) 243-3907| info@uni-bell.org

  2. PVCVSHDPEPRESSUREPIPEFORWATERMAINS PVCvsHDPEPressurePipeComparisonSheet 02.03.16 Uni-Bell PVC Pipe Association | 2711 LBJ Freeway, Suite 1000 | Dallas, TX 75234 Phone: (972) 243-3902 | Fax: (972) 243-3907| info@uni-bell.org

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