Examples Where Backflow Incidents Occurred
- In 1932, in the worst case in Nebraska history, during a 5-week period more than 10 percent of the 347 children in Huskerville, NE contracted polio. A study of the water revealed that the afflicted children lived in areas where flush valve water closets lacked vacuum breakers. A time relationship was found also in places where extreme fluctuations of pressure in the water mains might have permitted wastewater to be forced in the drinking water supply.
- Eighty students at a midwestern university reported remittent fevers, malaise, headache and anemia. Their symptoms led to a diagnosis of undulant fever (brucellosis). Only those students who had been working in the cultivation of bacteria in one of the laboratories were affected. The mystery was how the brucella cultures in the laboratory could have been transmitted to the students. Finally, a hose was found connected to a faucet in the laboratory. The other end of the hose was submerged in water containing brucella. A temporary reversal of pressure, possibly the consequence of a demand for water in another part of the system, had drawn the water teaming with brucella into the drinking water supply. Of the 80 students affected, one died. As you can see, the problem we are dealing with can have deadly results.
- In 1972 in a west coast industrial plant, a submerged inlet was used to supply a lye vat with water. On the other side of a wall from the vat was the employee's shower room. Fortunately, the cross connection was discovered before harm was done. However, company officials were alarmed that employees could have been taking showers with water contaminated with lye from the vats.
- In a case involving an automatic car wash, gallons of concentrated detergent were injected into a city water system. The detergent was found in resident's drinking water more than a block away. The cause was reported as an unprotected cross connection in the car wash plumbing lines.
- In Newton, Kansas in 1942, one of the town's two water supply mains had been taken out of service on September 2, 7, and 8. A house service connection to this main supplied three frost-proof hydrants, and two frost-proof toilets. It was assumed, from subsequent events that some unknown person or persons tried to obtain water from a hydrant connected to the main out of service. When no water flowed the person evidently left, leaving the valve open. On September 10, it was discovered that a neighboring sanitary sewer was clogged and the sewage had overflowed into the hydrant box. It was learned that for two days, all the sewage from the toilets of ten families had been permitted to flow into the water main. When the main was put back into service, there was no attempt to sterilize it. More than 2,500 persons in all parts of the town suffered enteric disorders as a result. Stool cultures and pathological findings from two autopsies diagnosed the illness as bacillary dysentery. In addition to the widespread illness in the town, it is believed that the infection was carried aboard a number of troop trains, which were watered in Newton at the time.
- Backsiphonage caused by defective plumbing in a new student nurses building was blamed for an outbreak of disease in 1963 in Ohio. It was necessary for 100 of the student nurses to be quarantined for two weeks. Bacteriological examination showed that the drinking water was contaminated. The city health commissioner theorized that salmonella was brought into the building by some of the girls and then spread by the defective plumbing.
- A tank truck filling from a city water supply caused a serious emergency involving the contamination of a water supply. In 1971, a contractor using a tank truck with a rig designed to pump and spray a mixture of water, fertilizer, grass seed and wood pulp working on the grounds of a subdivision. The contractor was using a direct connection to a fire hydrant to fill the tank with water, which was then mixed with the fertilizer and other ingredients. A high-pressure pump then mixed the fertilizer and other ingredients. A high-pressure pump then sprayed the mixture onto the ground. As the wood pulp circulated through the tank piping system, it plugged one of the lines while the pump continued to run, creating a very high pressure in the tank. This pressure was higher than the water supply system pressure and forced the solution of fertilizer into the water supply. Several people in the subdivision became ill after drinking the water, but the contamination was discovered and quick action in flushing and disinfecting the lines eliminated the danger.
- Even caddies experienced nausea, severe vomiting, and abdominal cramps after consuming a "soft drink" at a New York golf club in 1964. The beverage was commercially prepared by the mixture of syrup with carbonated water in a vending machine. Investigation revealed that a pipe carrying water into the machine was connected to the recirculating hot water system instead of the drinking water system. The day before the incident, a lye and chromate solution was added to the hot water system.
- A New England town had two separate water systems - one for safe drinking water and the other for fire protection. The fire protection system pumped untreated water directly from a river. At an industrial plant in town, workers mistook a fire system line for a fresh water line and connected a bubbler to it. After drinking the water from the bubbler, seven people developed infectious hepatitis and over a hundred people were ill with gastroenteritis.
- In 1967, an outbreak of gastroenteritis occurred at a small private college in Pennsylvania. Almost one quarter of the 700 students and faculty were affected. The only factor in common to all those who became ill was the consumption of water or food that had been prepared using water from the school water system. Investigation of the water system revealed that a water line had broken in the kitchen of the school cafeteria, flooding both the kitchen and the cafeteria. Cross connections were found between the sewage system and the water system that could have resulted in backsiphonage of sewage into the water system as a consequence of negative pressure during the break in the water line. It was concluded that the outbreak probably resulted from the presence of Shigella Sonnei in the water system. The incoculum would have been of sufficient size to overcome the chlorine in the water.