BACKFLOW PREVENTION - SPRINKLER TALK

1 Cross-Connection Control HandbookBACKFLOW 7/9/07 1:58 PM Page 1 Man has long recognized theneed for pure drinking water,but only in the last 50 or 60years has there been any realeffort to prevent contaminationcaused by double check valvescame into use around the turnof the century to isolate firemains and industrial water linesfrom the potable water supply,little interest was shown in theindividual treatment of plumb-ing 1929 the major breakthroughcame when a device consistingof two check valves with arelief valve between them wassuccessfully tested in Danville,Illinois. However, this valve wasnot produced commercially andit was not until the late 1930 sthat the real development ofeffective vacuum breakers andbackflow preventers took was in this period that ordi-nances for cross-connectioncontrol began to be Safe DrinkingWater Act, signed into law byPresident Ford, placed moreemphasis on the responsibilityfor drinking water need for cross-connectioncontrol exists in all types ofpremises, whether industrial orresidential.

2 BACKFLOW preventiondevices help protect the publicsafety by preventing potablewater contamination in suchcritical areas as municipalwater systems, food processingplants, medical and dentalwater supplies, and manyindustrial What is it? .. 1 Case Histories .. 2 - 3 Typical Cross-Connections .. 4 - 5 BACKFLOW PREVENTION Devices .. 6 How BACKFLOW PREVENTION Devices Work .. 7 Device Selection .. 8 Installation .. 8 - 9 Testing .. 9A Brief History ofCross-ConnectionControlBibliography Cross-Connection ControlManual (EPA-570/9-89-007) Environmental ProtectionAgency, Water Supply Division,Washington (1973)Recommended Practice forBackflow PREVENTION andCross-Connection Control,AWWA M14, American WaterWorks Association, Denver,CO, 1990.

3 Manual of Cross-ConnectionControl, Foundation forCross-Connection Control andHydraulic Research, Universityof Southern California;Los Angeles, Calif. 90007 American Society of SanitaryEngineering (ASSE), ProfessionalQualification Standards, BACKFLOW PREVENTION Assemblies- Series 5000, Bay Village, Standards Association,Manual for Selection,Installation, and Field Testing, informative booklet, for thepurpose of a better disseminationof the facts about potential hazards to public health throughbackflow 7/9/07 1:58 PM Page is it? BACKFLOW ? You may have heardof it, and you may understandsome of what it involves. Thisbooklet will help you to under-stand it better; exactly what itis, and how to prevent is the undesirablereversal of the flow of water ormixtures of water and otherundesirable substances fromany source (such as usedwater, industrial fluids, gasses,or any substance other than theintended potable water) intothe distribution pipes of thepotable water system.

4 Thereare two types of BACKFLOW con-ditions: backpressure andbacksiphonage. Backpressure: Occurs whenthe user system is at a higherpressure than the supply watersystems allowing undesirablesubstances to be pushed back into the potable watersystem. Some causes are:booster pumps, potable watersystem connections for boilers,interconnection with other pip-ing systems operating at higherpressures, or higher elevationsin user systems such as high-rise buildings. One specific example of thiswould be a steam heating sys-tem with the make-up waterline piped directly into the boil-er. The higher pressure in theboiler could force the chemical-ly treated boiler water backthrough the make-up water lineand into the potable water : Occurs whennegative or reduced pressureexists in the supply pipingallowing undesirable sub-stances to be drawn into thepotable water supply.

5 Somecauses are:undersized supply piping, sup-ply line breaks, reduced supplysystem pressure on the suctionside of an on-line boosterpump, or sudden upstreamhigh demand. An example ofthis is a child drinking milk witha straw. The child sucks onthe straw and the milk flows upthe straw and into the child smouth. What the child is actu-ally doing is creating a subat-mospheric pressure in hismouth and the atmosphericpressure ( at sea level)is pushing down on the surfaceof the milk and forcing the milkup the straw and into thechild s is one other very impor-tant term that must be under-stood before we can term is Cross-Connection, and it is defined as any actualor potential connectionbetween a potable water sys-tem and any other source orsystem through which it is pos-sible to introduce into thepotable system any used water,industrial fluid, gas, or othersubstance other than theintended potable water withwhich the system is arrangements, jumperconnections, removable sec-tions, swivel or change-overdevices and other permanentor temporary devices throughwhich, or because of which.

6 BACKFLOW can or may occurare considered to be WaterBoilerMake-UpWater 7/9/07 1:58 PM Page 3 All of this is very interesting,but does it REALLY happen? you may ask. The answer tothat is an emphatic YES! Beloware listed some typical cases ofbackflow that No. 1 The year was 1933. Peoplefrom all over the world werecrowding into one of America slargest cities to see the World s Fair. An epidemic ofAmoebic Dysentery broke outand official records show that98 people died and 1,409 oth-ers became seriously , possibly thousandsof other affected people werenever counted by investigatingagencies since when theybecame ill, they went home. Aspecial investigating committeeof public health authoritiesfound the main reason of thiscatastrophe to be.

7 Old andgenerally defective plumbingand cross-connections poten-tially permitting backsiphonagefrom fixtures, such as bathtubsand Case No. 2In December, 1964, a hospitalin the State of Michigan had itspotable water system contami-nated. The cause was anunprotected autopsy table inthe hospital s No. 3It was in July of 1955 in SanPedro, California, a NavyDestroyer pumped salt waterthrough five obsolete checkvalves into the street mains in a90 square block of the town. Case No. 4 This unusual death was causedby backsiphonage in a suburbof one of California s largestcities. A man was spraying hislawn with a commercial weedkiller that contained an arseniccompound. His applicator wasan aspirator device on his gar-den hose, to which wasattached a bottle of the arsenicpoison.

8 When he had finishedspraying, the man turned offthe hose, disconnected theapplicator, and since it was awarm day, turned the hose onagain to get a drink of water. Ashort time later, he was deadfrom arsenic poisoning. Atsome time while he was spray-ing, a backsiphonage conditionhad occurred and the arsenicwas carried back into the No. 5In 1969 in Utah, raw irrigationwater was pumped through afarm standby irrigation connec-tion into over half of the entiretown s potable water standby connection wasnot protected with a backflowprevention HistoriesCity 7/9/07 1:58 PM Page 4 Case No. 6In August, 1969, 83 footballteam members and coachingstaff were stricken with infec-tious hepatitis due to subsur-face hose bibs and a nearbyfire.

9 The fire trucks in fightingthe fire reduced the main pres-sure enough to cause back-siphonage from the hose No. 7In the summer of 1970 in NewJersey, a soft drink vendingmachine in the Caddy house ofa golf club was connected tothe building heating system inwhich hexavalent chromiumhad been added. Eleven casesof nausea were reported by HistoriesCity MainHeating SystemLine Treated with aHexavalent 7/9/07 1:58 PM Page 5 Spray Hose in Sink This type of cross-connectionis commonly found in the foodindustry and in janitor s sinks. Ahose has been connected tothe faucet on the sink. Whenthe faucet is left running, a lossin pressure of the supply maincan siphon this used waterback into the potablewater InletsIn many industrial installationsthat use chemically treatedbaths, the make-up water lineruns directly into the tank.

10 Ifthere is backsiphonage, thetoxic chemicals can be suckedback into the potablewater BibsAt first glance, a hose bibseems innocuous, but it is thethings people do with the hosethat creates problems. In thisexample, a man is trying toblow a stoppage out in a sewerline, but with a sudden drop inline pressure, this contaminatedwater can be backsiphonedinto the potable water LineMake-UpWater 7/9/07 1:58 PM Page 6 Lawn SprinklersOn a large number of lawnsprinkler installations, thesprinkler head is below theground level. Water which mayhave been in contact with fertil-izers and weed killers can thenbe backsiphoned through aleaky valve into the potablewater SystemsOn many farms water ispumped from irrigation waterchannels into the SPRINKLER sys-tem.