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Government and Institutional Sites
Medical Sites

  • In 1982 in Illinois, ethylene glycol back siphoned from an air conditioning system ’s water holding tank
    into a group of dialysis machines, contributing to the death of several” (number not given) patients
    (AWWA PNWS, 1995).

  • During shut-down of a water main to repair a valve in 1984, the backflow of water from a nursing home’s
    boiler caused burns to a water department employee’s hands in Washington State (AWWA PNWS, 1995).

  • In 1994, during repairs to a nursing home air conditioning unit in Franklin, Nebraska, a hole left in the
    cooling coils allowed Freon to backflow into the city water main, affecting the city’s 1,100 residents.
    Customers complained about the taste of the water, but no illnesses were reported (AWWA PNWS,

Schools, Universities, and Children’s Camps

  • In 1990, six staff members of an Indiana middle school reported becoming ill after drinking water
    containing ethylene glycol that backflowed from the school’s cooling system into the potable water
    system (AWWA PNWS, 1995).

  • In 1987, copper sediment contamination in a beverage mixing tank resulted in four cases of illness in a  
    residence hall at Michigan university (AWWA PNWS, 1995).

  • In 1995, three people became ill at a California school after drinking water from a system with a double-
    check backflow prevention valve that did not meet industry standards and had badly deteriorated rubber
    gaskets (Craunand Calderon, 2001).

Public Water Systems

  • In 1984, creosote was backsiphoned through a three-quarter inch hose used to prim e a pump,
    contaminating a section of a Georgia community water system. No illnesses were reported (AWWA
    PNWS, 1995).

  • In 1970 in Mattoon, Illinois, hot wash water from an asphalt plant backpressured into mains during flow
    testing of fire hydrants (USC FCCCHR, 1993).

Other Government/ Institutional Sites (e.g.,public buildings, churches)

  • In 1976, water fountains at the State Capitol building in Salem, Oregon, were contaminated with freon
    gas from a ruptured heat exchanger. The gas combined with the fluoride in the water supply, forming an
    acid compound that caused a bitter, burning taste (AWWA PNWS, 1995).

  • In 1991, two check valves froze open at a Texas Air Force base, resulting in a back flow from a water
    chiller; pathogenic bacteria were detected in the water. The specific contaminant was not identified.
    Approximately 2,000 workers and residents were without water during system flushing (AWWA PNWS,

  • In 1994, the water system at a Tennessee prison was cross-contaminated by the facility’s wastewater
    pump station, resulting in 304 cases of giardiasis (Craun and Calderon, 2001).

  • Purified drinking water lines at the Oak Ridge Reservation’s K-25 atomic bomb fuel plant were
    interconnected for an unknown length of time (possibly on the order of decades) with lines carrying
    impure creek water. The creek water contained poisons generated from nuclear fuel production, possibly
    including contaminant s such as strontium -90 and arsenic (Nashville Tennessean, 2000).

Commercial Sites / Restaurants

  • In 1979, two high school students in Seattle, W A, became ill, showing symptoms of copper poisoning
    after drinking soft drinks from a dispensing machine in a restaurant. The backflow of carbon dioxide from
    the soft drink dispensing machine was considered the likely cause of the copper release (AWWA PNWS,

  • In 1987, a child in Minnesota suffered acute copper toxicity when backflow from a carbon dioxide
    machine contaminated a restaurant's potable system (AWWA PNWS, 1995). Office Buildings

  • In 1989, a backflow event at an Ohio government office building occurred after crews worked on the air
    conditioning system. Twelve individuals became ill after ingesting water that had been contaminated with
    Acid Blue 9, an algae-retarding chemical (AWWA PNWS, 1995).

  • In 1991, trichloroethane entered the distribution system of a city in Missouri from a newspaper office.
    Uncoordinated flushing by the water system caused the contaminant to spread throughout the system ,
    with concentrations as high a s 420 microgram s/L (AWWA PNWS, 1995).

Other Commercial Sites

  • In 1974  backsiphonage of a chromium compound from the chiller water of an air conditioning system
    contaminated the drinking water system in the auditorium hosting the 94th annual AWWA conference
    and exhibition in Massachusetts, involving thousands of people (AWWA PNWS, 1995).

  • In 1990, 1,100 guests of a Tennessee racquet and country club became ill with an intestinal disorder
    after consuming the club 's contaminated water supplied from an unauthorized and unprotected auxiliary
    well in close proximity to a malfunctioning sewage pumping station (AWWA PNWS, 1995).

  • In 1994, a number of individuals attending an Ohio convention got sick with giardiasis, spread by an ice
    machine contaminated by a cross-connection to a sewage drain (AWWA PNWS, 1995).

Miscellaneous Sites / Agricultural Sites

  • In 1991, an antibiotic solution used at a commercial chicken house entered an Arkansas public water
    system as a result of a cross-connection between an auxiliary well connected to the chicken house
    plumbing (AWWA PNWS, 1995).

  • In 1995, pesticides (paraquat and atrazine) were backsiphoned into a distribution system when an
    accidental water main cut occurred while a Louisiana farmer was diluting herbicides in a tank. Some
    people reported nausea, stomach burns and pains, profuse sweating, diarrhea, and shortness of breath.
    The incident was the subject of a class-action lawsuit (AWWA PNWS, 1995).

Recreational Sites

  • In 1986 in Springfield, MO, failure of a single check valve on a soft drink dispensing machine at a local
    fair resulted in the backflow of carbon dioxide that created levels of 2.7 mg/L of copper and 2.2 mg/L of
    zinc. Three people experienced vomiting and abdominal pain (AWWA PNWS, 1995).

  • In 2000, contaminated water lines at an Ohio fairground resulted in an outbreak of E. co li, resulting in 30
    cases of illness (Cleveland Plain Dealer, 2001).

Industrial Sites

  • In 1989, backpressure from a propane tank car forced propane into the water supply of Fordyce,
    Arkansas. Three people in separate buildings were injured from explosions after flushing toilets, and two
    houses were destroyed and a business was damaged by explosions and subsequent fires (AWWA
    PNWS, 1995).

  • In 1990, at least two individuals became ill after an unknown quantity of industrial chemicals backflowed
    into the public water supply via an unprotected auxiliary line illegally tapped to a hose connected to the
    plant’s flushing system. The incident occurred at a New Mexico facility that transforms wheat and barley
    into ethanol (AWWA PNWS, 1995).

Other Sites/ Site Type Unknown

  • In 1980, a cross-connection aboard an Alaskan crab processing ship resulted in backflow of sewage
    (including Giardia), causing 189 employees to become ill and endangering about $35 million worth of
    processed king crab (USC FCCCHR, 1993; CDC, 1982 ).
EPA Documented Backflow Case Studies
All Backflow Services of Brevard A Division of WRC Management