Examples of Backflow

In Roanoke, Virginia on October 1979 Chlordane, a highly toxic insecticide, was backsiphoned into the water supply. This occurred while the water department was repairing a water main. An employee from an exterminating working at a home nearby left one end of a hose connected to an outside faucet and the other end in a barrel of diluted insecticide. During the water service interruption, the chlordane was backsiphoned into the house plumbing and the city water main. The city performed extensive flushing of the water mains but the insecticide had adhered to the inside of the pipes. Tests of the water taken six days after the contamination showed Chlordane levels five times greater than considered safe. Residents of the effected area either carried water to their houses from 400 gallon water tanks the city supplied or traveled to homes of friends or relatives to shower and eat meals.

 

In December 1970, wine backflowed into the public water system in Cincinnati, Ohio. At a winery in the City, someone inadvertently left open a water valve to a wine distilling tank after flushing out the tank. During a subsequent fermenting process, wine backflowed from the tank into the city water mains and out of the faucets of nearby homeowners. This reversal of flow through the water piping occurred because the pressure in the wine distilling tank was greater than the pressure in the City water 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. There was a water main break, which caused a vacuum in the public water system. The vacuum in the public water system (backsiphonage) pulled dirty ground water and nematodes (worms) from an 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.