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OFFICE:
395 West Avon Rd.
Avon, Ct 06001
Tel: 860-521-7484
Fax: 860-404-1777
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Case Histories
BACKFLOW AT A PREMISES WHERE THE CONSUMER'S POTABLE WATER SYSTEM SUPPLIES AN IRRIGATION PIPING SYSTEM
On October 1, 1991, two homeowners in the City of Southgate, Michigan, found parasitic worms, or nematodes, in their water. One homeowner found the worms swimming around in his bathtub when he started filling the tub for his child. He also found rust and other debris in his water. The Wayne County Health Department determined that water had backflowed through a residential irrigation system into the public water system.
An atmospheric vacuum breaker on the residential irrigation system had malfunctioned because the device's air inlet valve had stuck to the device's air inlet port. There was a water main break, which caused a vacuum in the public water system. The vacuum in the public water system sucked some water--and some nematodes--from the irrigation system into the public water system.
Crews from the City's Department of Public Services opened fire hydrants and flushed all the water mains located three blocks north and south of where the backflow incident occurred. Analysis of subsequent water samples collected by the Department of Public Services showed no detectable coliform bacteria.
The County cited the owner of the irrigation system for improper installation of the system. The contractor that this resident employed to install the irrigation system did not have a City permit and used a "cheap" atmospheric vacuum breaker.
BACKFLOW AT A CAR WASH FACILITY
On February 12, 1979, many residents in the Greenwood District of Seattle, Washington, began complaining about "grey-green and slippery," "muddy," or "soapy" water. One resident brought a water sample to the Seattle Water Quality Laboratory. Preliminary analysis of this sample showed that the water was contaminated with a detergent solution. The Seattle Water Department dispatched an emergency field crew to initiate flushing of hydrants in the affected area. Investigation revealed that recycled wash/rinse water at a large car wash facility had backflowed into the public water system.
On February 10, a high-pressure pump at the car wash facility broke down. This pump was used to pump recycled wash/rinse water to the initial/scrubber cycle of the car wash, which was not normally connected to the potable water system at the car wash. After the pump broke down, workers kept the car wash operating by connecting a two-inch-diameter hose between piping in the rinse cycle of the car wash, which was directly supplied with water by the car wash's potable water system, and piping in the scrubber cycle.
On February 12, the owner of the car wash facility repaired the high-pressure pump and turned it on. However, nobody removed the hose connection between the rinse-cycle piping and the scrubber-cycle piping. Unbeknown to car wash personnel, the high-pressure pump forced a large quantity of recycled wash/rinse water through the hose connection, the rinse-cycle piping, and the car wash's potable water system into the public water system. This recycled wash/rinse water was, in turn, distributed to the potable water systems of homes and commercial establishments in the surrounding area. Sometime later, a car wash employee flushed the toilet in the car wash's rest room and noticed brown soapy water in the toilet bowl. Car wash personnel quickly realized that they had created a cross-connection and removed the hose between the rinse-cycle piping and the scrubber-cycle piping.
After finding the source of the soapy water problem, the City Water Department conducted water main flushing to intercept and limit the scope of the contamination. Because of its prompt response, the City Water Department confined the contamination to an eight-block area. Nevertheless, the City Water Department delivered a public notification statement to six radio and television stations. Two people in the contaminated area reported illness after drinking the water, but investigations by the Seattle-King County Health Department epidemiologist were unable to authenticate either report.
The City Water Department ordered the owner of the car wash facility to install a reduced-pressure principle backflow-prevention assembly in the potable water service connection to the car wash. The owner complied within 24 hours.
BACKFLOW AT A DENTAL OFFICE
Several residents in a community in central Kansas were experiencing air in their water. Employees of the water department traced the source to a dental office.
An air compressor at the dental office supplied air at 80 psig to dental equipment. The water pressure in the public water system varied from 40 to 45 psig. A solenoid valve that isolated the air supply from the potable water system malfunctioned. Consequently, the air compressor was trying to keep 80 psig of air in the entire public water system.
The water department required the dentist to install a reduced-pressure principle backflow-prevention assembly at the water service connection to the dental office.
BACKFLOW AT A CLINIC
On November 17, 1993, the Wilson, North Carolina, Water Distribution Division received a complaint from a clinic. The clinic was complaining about a strange, bitter taste and strong chemical odor to its water. Upon investigation, the City Water Distribution Division discovered that chemicals from a mixer used in x-ray development had backflowed into the clinic's potable water system.
A chemical mixer used in x-ray development at the clinic combined water with chemicals--developer and fixer. Water was added to the mixer using a garden hose connected to a hose bibb. Someone submerged the end of this garden hose in the mixer and, thus, created an indirect cross-connection. A hose bibb vacuum breaker was not in place on the hose bibb as required by code, although such a device had been in place when the local building department issued the final certificate of occupancy for the clinic.
On November 15, 1993, City Water Distribution Division personnel, working with a utility contractor, cut a section from the eight-inch-diameter water main in front of the clinic to replace a leaking tapping sleeve with a tee. They did this work during evening hours because the clinic would lose water service temporarily. While this work was being done, a negative pressure apparently developed in the water supply piping to or in the clinic. As a result, the chemicals in the mixer were backsiphoned through the garden hose mentioned above and into the clinic's potable water system.
BACKFLOW AT A PLATING PLANT
On June 14, 1987, the employees at an electroplating plant in Kitchener, Ontario, noticed that the water from a plant drinking fountain "looked like Kool-Aid" and had a metallic taste. By June 19, 29 workers reported being exposed to nickel contamination. Eleven workers were in the hospital, and six workers were under observation by a family doctor.
The nickel most likely entered the plant's potable water system by backsiphonage through a submerged inlet to a plating rinse tank. On June 14, the plant shut down its potable water system for repair work. There was no backflow preventer in the potable water line supplying the plating rinse tank.
BACKFLOW AT A VETERINARY OFFICE
On June 23, 1983, the City of Calgary, Alberta, received complaints from several homes about poor tasting water flowing from their taps. The City had its waterworks division collect water samples and forward them to a laboratory for analysis. Analyses showed high plate counts in some samples and detectable traces of Escherichia coli in one sample. As a result, the City had its water works division immediately begin flushing water mains in the area and dispatched plumbing inspectors to find out if a cross-connection was responsible for the detection of Eschericia coli. After water mains in the area were flushed for several hours, the City collected new water samples. Analyses of these samples showed lower plate counts, but Escherichia coli was still detectable in the samples. After a 32-hour investigation of premises within the area, plumbing inspectors found several cross-connections at a veterinary office.
The City ordered the installation of backflow-prevention assemblies at the veterinary office. Analyses of water samples collected after installation of the assemblies showed no evidence of water contamination.
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