Backflow Cases

Backflow at an Agricultural Premises

Date of Backflow Incident: June, 1983

Location of Backflow Incident: Woodsboro, Maryland

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - U.S. Environmental Protection Agency, Cross-Connection Control Manual, 1989. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

In June 1983, "yellow gushy stuff" poured from some faucets in the town of Woodsboro, Maryland. Town personnel notified the County Health Department and the State Water Supply Division. The State dispatched personnel to take water samples for analysis and placed a ban on drinking the town's water. Firefighters warned residents not to use the water for drinking, cooking, bathing, or any other purpose except flushing toilets. The town began flushing its water system. An investigation revealed that the powerful agricultural herbicide Paraquat had backflowed into the town's water system.

Someone left open a gate valve between an agricultural herbicide holding tank and the town's water system and, thus, created a cross-connection. Coincidentally, water pressure in the town temporarily decreased due to failure of a pump in the town's water system. The herbicide Paraquat was back-siphoned into the town's water system. Upon restoration of pressure in the town's water system, Paraquat flowed throughout much of the town's water system.

Fortunately, this incident did not cause any serious injury or death. The incident did, however, create an expensive burden on the town. Tanker trucks were used temporarily to provide potable water, and the town flushed and sampled its water system extensively.

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Backflow at a Beverage Bottling Plant

Date of Backflow Incident: December, 1987

Location of Backflow Incident: Spokane, Washington

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995

Case History:

On December 31, 1995, the Spokane, Washington, Water Department received complaints about air in the water and dispatched crews to the scene to flush the water mains. Upon investigation, the City Water Department discovered that a compressor at a soft drink bottling plant had injected air into the public water system.

Personnel at the bottling plant said that a potable water line into a shop area froze often during winter and that they used compressed air to clear the line. Workers normally closed isolating valves before attempting to clear the line, but they forgot to close the valves this time. Consequently, a large amount of air was injected into the public water system surrounding the bottling plant.

The Water Department required the installation of a reduced-pressure principle backflow-prevention assembly at the bottling plant to prevent recurrence of the problem.

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Backflow at a Car Wash Facility

Date of Backflow Incident: February, 1979

Location of Backflow Incident: Seattle, Washington

Source(s) of Information: American Water Works Association, Recommended Practice for Backflow Prevention and Cross-Connection Control, AWWA Manual M14, Second Edition, 1990 - Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - U.S. Environmental Protection Agency, Cross-Connection Control Manual, 1989. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

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 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 late, a car wash employee flushed the toilet in the car wash's restroom 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.

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Backflow at a Chemical Plant

Date of Backflow Incident: October, 1986

Location of Backflow Incident: Lacey's Chapel, Alabama

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - U.S. Environmental Protection Agency, Cross-Connection Control Manual, 1989. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

On Wednesday, October 8, 1986, an eight-inch diameter water main of the Bessemer Water Service broke in Lacey's Chapel, Alabama. While repairing the water main, one Bessemer Water Service worker suffered leg burns from an unidentified chemical and required medical treatment.

Wednesday night and early Thursday, the Bessemer Water Service received several complaints from the area of Lacey's Chapel served by the broken water main. Some residents complained of burned throats or mouths after drinking the water. Tiny red blisters covered one residents body after he got out of the shower on Thursday morning. He and several other residents received medical treatment at the emergency room of the local hospital. The Bessemer Water Service shut down the water service to the area at 7:00 A.M. on Thursday and initiated an investigation. Sodium hydroxide, a caustic chemical, had backflowed into the public water system from a nearby chemical plant.

The chemical plant distributed chemicals such as sodium hydroxide. Sodium hydroxide was brought to the plant as a liquid in bulk tanker trucks and was transferred to a holding tank and then pumped into 55-gallon drums. When the water main broke on Wednesday, a truck driver was adding water to a tanker truck that had carried sodium hydroxide. On this occasion, the driver was filling the tanker from a connection at the bottom of the tanker. Consequently, the sodium hydroxide in the tanker was backsiphoned into the public water system when the water main broke.

About 60 homes in the area of the broken water main received contaminated water. Measurements of pH were as high as 13 in some homes. The Bessemer Water Service flushed water mains, and health officials made sure that all plumbing was flushed.

There was no backflow preventer at the water service connection to the chemical plant. The Bessemer Water Service did not have a cross-connection control program although State regulations required public water systems to have such a program.

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Backflow At a Clinic

Date of Backflow Incident: November, 1993

Location of Backflow Incident: Wilson, North Carolina

Source(s) of Information: Drinking Water and Backflow Prevention, Volume 11 Number 22 (February 1994) - Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995.

Case History:

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 with 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 back siphoned through the garden hose mentioned above and into the clinic's potable water system.

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Backflow at a Dairy

Date of Backflow Incident: September, 1979

Location of Backflow Incident: Portland, Oregon

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995

Case History:

On September 18, 1979, a concrete plant in Portland, Oregon, reported foamy water at the plant. The Portland Water Bureau took water samples at the plant and at three fire hydrants in the area. All but one of these samples showed the presence of a foaming agent. Accordingly, the City Water Bureau dispatched crews to flush mains in the area. After investigation, the City water Bureau concluded that a detergent solution at a dairy had backflowed into the public water system.

City Water Bureau personnel suspected that the dairy was the source of the foaming agent because a detergent solution had backflowed from the dairy in 1970. The dairy had installed a reduced-pressure principle backflow-prevention assembly in each of its two water service connections in 1971. Each of these assemblies had passed its last annual performance test in February 1979. However, performance tests of the assemblies in response to the September 18 incident showed that both assemblies were in poor condition. Indeed, one assembly completely failed the last performance test.

Technicians repaired both of the dairy's reduced-pressure backflow-prevention assemblies by replacing the disks, the gaskets, and all worn parts in these assemblies.

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Backflow at a Filming Location

Date of Backflow Incident: October, 1994

Location of Backflow Incident: Los Angeles, California

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995

Case History:

In October 1994, a filming company was filming at a ranch in Los Angeles, California. In the scene that the company was filming, it was snowing. The crew was spraying artificial snow from a pressurized 55-gallon tank of Macrojet I Concentrate. The truck that furnished water for generation of the artificial snow failed to work properly. Therefore, a special effects person connected3d a garden hose between the tank of Macrojet I Concentrate and a hose bibb at the ranch. When the special effects person opened the hose bib, the pressure in the tank forced the chemical through the ranch's potable water system into California-American's public water system.

Residents on the same cull-de-sac as the ranch began calling California-American and complaining about brown soapy water coming from their faucets. California-American employees instructed the consumers to flush both hot and cold water through their faucets until the water ran clear. Meanwhile, California American flushed its system for several hours until the water ran clear and supplied bottled water to the homes in the area. The water company continued flushing its system for several more hours during the next day until the water was safe to drink.

Filming companies often used this ranch for filming, and California-American wanted to avert future problems. Consequently, California-American required the ranch owner to install a reduced-pressure principle backflow-prevention assembly on the water service connection to the ranch.

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Backflow at a Fire Protection System

Date of Backflow Incident: June, 1979

Location of Backflow Incident: Meridian, Idaho

Source(s) of Information: American Water Works Association, Recommended Practice for Backflow Prevention and Cross-Connection Control, AWWA Manual M14, Second Edition, 1990 - Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995.

Case History:

On June 18, 1979, residents in the city of Meridian, Idaho, complained that their water had an odor and taste of onions. At this time, the City was routinely flushing fire hydrants in the area of the complaints. The City could not see a consistent pattern to the odor or the complaints.

By isolating potions of the water system and conducting a premises-by-premises inspection, the City narrowed the source of the odor to one area containing a supermarket, a car wash, and a church printing firm. When the City flushed the nearest fire hydrant, the odor became very strong. Inspection revealed that an alarm check valve on a fire sprinkler system in the supermarket was leaking and allowing stagnant water to backflow from the sprinkler system into the public water system.

When the pressure in the public water system was reduced during fire hydrant flushing, the alarm check valve on the fire sprinkler system at the supermarket would leak, but the check valve would not open enough to set off the alarm. The City turned off water service to the supermarket fire sprinkler system, and the odor and taste problem did not occur during hydrant flushing.

Analysis of water samples taken from the supermarket fire sprinkler system showed Clonothrix fusa and Zoogleora ramigera bacteria in sufficient concentration to cause the onion odor and taste problem.

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Backflow at a Gas Tank Maintenance Facility

Date of Backflow Incident: March, 1989

Location of Backflow Incident: Fordyce, Arkansas

Source(s) of Information: Pacific Northwest Section of the American Water works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - U.S. Environmental Protection Agency, Cross-Connection Control Manual, 1989. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

In March 1989, propane gas backflowed into the public water system in Fordyce, Arkansas. Explosions and subsequent fires destroyed two houses and seriously damaged a local business. Three people in the subsequent buildings were injured when explosions occurred after they flushed toilets. Investigation revealed that the gas had backflowed through a cross-connection between the public water system and a railroad tank car.

A nearby company cleaned and refurbished railroad cars and routinely worked on tank cars that carried propane, methane, or ammonia. When workers found propane in the tank car, they bled the gas off through a tower and burned the gas. Then the workers injected steam, water and air into the tank car to clean it. Apparently, workers accidentally connected a water hose between the company's potable water system and a railroad tank car still containing pressurized propane. The pressure in the tank car was greater than the pressure in the City's potable water system and, thus, forced propane gas into the water system.

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Backflow at an Industrial Facility

Date of Backflow Incident: May, 1988

Location of Backflow Incident: Edgewater, Florida

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - U.S. Environmental Protection Agency, Cross-Connection Control Manual, 1989. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

On Friday, April 29, 1988, it was reported that the potable water system at a paint factory in the City of Edgewater, Florida, had been contaminated by a chemical, propylene glycol. The contamination had actually occurred Thursday afternoon but was not reported until Friday afternoon. The production manager at the factory thought the chemical contaminant was confined to the factory's potable water system. He had shut off the factory's water service connection to the City's public water system and had flushed the factory's potable water system. The Florida Department of Environmental Regulation ordered a ban on water usage throughout the City as a precaution, and the City notified its 5,700 water customers not to use tap water for drinking, cooking, or bathing.

The paint factory used propylene glycol to keep paint from breaking down after exposure to weather. The contamination occurred when a valve at the factory malfunctioned causing the chemical to flow into the factory's potable water system.

Propylene glycol can irritate the eyes and skin upon contact. Although it is relatively non-toxic, it can cause heart and urological damage if consumed in large5large doses. Analysis of samples collected Friday from the City's potable water system did not show the presence of propylene glycol. No one sought medical aid from the local hospitals for an illness related to the consumption of contaminated water.

The City ordered that a double check valve backflow-prevention assembly be installed at the water service connection to the paint factory.

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Backflow at a Laboratory

Date of Backflow Incident: October, 1989

Location of Backflow Incident: Edmonton, Alberta, Canada

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - U.S. Environmental Protection Agency, Cross-Connection Control Manual, 1989. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

On October 5, 1989, staff at a laboratory and offices of a research facility in Edmonton, Alberta, noticed a smell coming from the hot water at the facility. A growth nutrient for microorganisms had backflowed from the laboratory into the facility's domestic hot water system.

Laboratory personnel were injecting a soupy, nontoxic fluid used as a growth nutrient into a fermenting vessel. Hot water, used for dilution, was directly cross-connected to this vessel. Because the injection pressure was greater than the pressure in the domestic hot water system, as much as 150 liters of the growth nutrient backflowed into the domestic hot water system.

Although the growth nutrient itself was not considered a health risk, the growth nutrient could have promoted the growth of any bacteria in the potable water system. Thus, the potable water system at the facility was chlorinated and flushed.

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Backflow at a Packing House

Date of Backflow Incident: October, 1979

Location of Backflow Incident: Marshalltown, Iowa

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

In October, 1979, $2,000,000 worth of pork was contaminated at a Swift and Company packing house in Marshalltown, Iowa. The meat became contaminated when employees unknowingly sprayed nonpotable water on hog carcasses during the normal cleaning process. Food safety and quality service officials concluded that a cross-connection had been created between the potable water system and the nonpotable water lines in the packing house. This cross-connection allowed waste water from the kill floor and water used to deodorize rendering operations to get into the potable water system.

The packing house was shut down for a long time while officials searched for the cause of the contamination, monitored decontamination and sterilization procedures, and decided what to do with the contaminated pork. Swift and Company reportedly spent more than $3,000,000 because of the problem, and 200 people were unemployed while the packing house was shut down.

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Backflow at a Paper Product Plant

Date of Backflow Incident: November, 1987

Location of Backflow Incident: Burnaby, British Columbia, Canada

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995

Case History:

On November 2, 1987, a break occurred in a municipal water main supplying water to industrial properties in the City of Burnaby, British Columbia. While the City was repairing the broken water main, dirty water discharged from the main into the excavation though isolating valves on the main were closed. Upon investigation, the City determined that the dirty water was coming from a paperboard plant along the Fraser River. The plant's only source of potable water was the municipal water main that was disrupted during the main repair. Hence, the City realized that the plant must have an auxiliary water supply and that water was backflowing from the plant's auxiliary water supply into the municipal water system.

The paperboard plant was maintaining two water systems. One system was a combined fire, industrial, and domestic system supplied with potable water from the Fraser River. To keep the plant in operation after the municipal water main break, plant workers connected a fire hose between the two systems. Consequently, river water was pumped through the plant's combined fire, industrial, and domestic water system into the municipal water system.

The City ordered personnel at the paperboard plant to remove the fire hose cross-connection, flush and disinfect the plant's domestic water system, and install a reduced-pressure principle backflow-prevention assembly at the plant's service connection from the municipal water system. City workers flushed and disinfected the municipal water main contaminated by the backflowing river water.

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Backflow at a Pest Control Company

Date of Backflow Incident: June, 1987

Location of Backflow Incident: Fair Lawn and Hawthorne, New Jersey

Source(s) of Information: Drinking Water and Backflow Prevention, Volume 11 Number22 (February 1994) - Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - Watts Industries, Inc.; Watts Regulator News/Stop Backflow

Case History:

On June 24, 1987, a construction crew inadvertently broke a water main while widening a bridge in New Jersey. Several hours after the water main was repaired, a customer called the water department to complain that the water was milky and smelled bad. Pesticides had backflowed into the public water system.

The backflow incident happened at the time the bridge construction crew broke the water main. Because of the water main break, a siphoning action occurred in the water mains. Concurrently, a pest control company employee was rinsing a tank that contained a weak solution of the pesticides heptachlor and chlordane. The hose that the employee was using had the pesticide Dursban on it. One to three gallons of the pesticides were sucked through the pest control company's potable water system and into the public water system.

Several people drank, and watered their lawns with, the contaminated water. Fortunately, however, there were no immediate illnesses or injuries. After receiving the complaint about milky and bad smelling water, the water department immediately shut off the water supply to the 63 customers affected by the water main break and notified them not to drink the water or use it to cook, bathe, or wash clothes.

The 63 homes and businesses went without usable water service for several days while affected water mains and plumbing were flushed and disinfected. A tank truck provided potable water for drinking and cooking. Shower facilities at the local public high school and middle school were made available for use by affected residents.

Because the pesticides stuck to piping, the plumbing at nine locations had to be replaced. At all other locations, analysis of water samples showed that the pesticides were not detectable.

The pest control company assumed responsibility for the backflow incident and paid for the necessary replacement of plumbing. Nevertheless, 21 homeowners sued the pest control company for $21,000,000. They claimed that the pest control company irreparably damaged plumbing fixtures, that residents continue to suffer physical injury, and that residents have been subjected to mental distress, inconvenience, and loss of property. In addition, residents asked the pest control company to pay medical expenses incurred because of the incident and to maintain a health surveillance program for affected residents.

The water department ordered the pest control company to cease operating until a backflow preventer was installed at the water service connection to the pest control company. Following installation of a backflow preventer, the pest control company resumed operating.

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Backflow at a Plating Plant

Date of Backflow Incident: June, 1987

Location of Backflow Incident: Kitchener, Ontario, Canada

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995.

Case History:

On June 14, 1987, the employees of 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.

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Backflow at a Poultry Farm

Date of Backflow Incident: June, 1991

Location of Backflow Incident: Casa, Arkansas

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

During the week of June 23, 1991, residents near a poultry farm in Casa, Arkansas, became concerned when their water appeared discolored. In response to complaints from one water customer, it was discovered that the public water system had been contaminated by backflow from a chicken house at the poultry farm.

Both the public water system and an auxiliary water well supplied water to the plumbing in the chicken house. The water service connection from the public water system to the chicken house included two single check valves in series for backflow prevention. Workers were using the water in the chicken house to administer an antibiotic solution to the chickens.

When the Casa water system manager became aware of the problem, the manager shut off water service to the chicken house and flushed the public water main serving the area. He later removed the water meter serving the chicken house until a proper backflow preventer could be installed.

The feeding of antibiotic solutions and live virus vaccines into water to treat and immunize chickens is a popular practice at poultry farms. Such antibiotic solutions could cause severe adverse effects in humans who are hypersensitive to drugs, and most of the virus vaccines used to immunize chickens are pathogenic to humans.

Therefore, poultry farms should be considered as a significant health hazard to public water systems, and a reduced-pressure principle backflow-prevention assembly should be installed at the water service connection to each poultry farm.

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Backflow at a Premises Where Potable Water Supplies A.C.

Date of Backflow Incident: July, 1989

Location of Backflow Incident: Cincinnati, Ohio

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995

Case History:

On July 27, 1989, the Health Commissioner's office in Cincinnati, Ohio, received reports of blue water in a government office building. An investigation found that an algae-retarding chemical had backflowed into the building's potable water system from the building's air conditioning system.

A blue liquid known as Acid Blue 9 was being used to prevent algae in the condenser of the government building's air conditioning system. A cross-connection existed between the building's air conditioning system and the building's potable water system. Backflow of the algae-retarding chemical occurred while crews were working on the air conditioning system.

The backflow incident apparently caused 12 illnesses. The Health Commissioner stated that anyone who drank from the drinking fountains in the building on July 27 or 28 could become ill with diarrhea or vomiting, especially after drinking alcoholic beverages.

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Backflow at a Premises Where Potable Water Supplies A Heat Exchanger

Date of Backflow Incident: February, 1984

Location of Backflow Incident: Riverbend, Oregon

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995

Case History:

On February 13, 1984, the Oregon Health Division received a call from a resident of a mobile home park in Riverbend, Oregon. The resident described his water as having an oily substance mixed with it. When a representative of the Oregon Health Division visited the home on February 15, there were no visible impurities in the home's tap water. However, the homeowner saved a sample of the oily water. The sample was cloudy white with a layer of yellow oil floating on the surface.

Evidence suggested that the problem was isolated to the individual home. Because only the hot water tap had produced the oily water, the home's hot water tank was drained to observe its contents. A slightly oily film was present on the surface of the water from the tank. The home had a solar hot water heating system, and the homeowner stated that the system had not been operating properly. Thus, the Oregon Health Division representative concluded that the solar hot water heating system was the probable source of the water contamination.

On February 17, an employee of a local heating company inspected the home's solar hot water heating system. The system used dichlorofluoromethane gas as the heat transfer medium and had a single-wall heat exchanger. Mineral oils were also used in the system. The piping used for circulating the gas heat transfer medium was filled with water. Apparently, the single wall separating the heat transfer medium from the domestic hot water in the heat exchanger had begun to leak and had created a cross-connection between the heat transfer medium circulating system and the domestic hot water system.

Dichlorofluoromethane is not considered toxic. However, the chlorinated compound is to be suspect from a health standpoint. Also, the public water system had no assurance that this solar hot water heating system would not be altered in the future to utilize a toxic heat transfer medium.

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Backflow at a Premises Where Potable Water Supplies an Irrigation System

Date of Backflow Incident: October, 1991

Location of Backflow Incident: Southgate, Michigan

Source(s) of Information: Drinking Water and Backflow Prevention, Volume 9 Number 6 (June 1992) - Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

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 the 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.

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Backflow at a Premises Where Potable Water Supplies a Water Boiler

Date of Backflow Incident: January, 1990

Location of Backflow Incident: Brighton, Colorado

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

On January 30, 1990, authorities closed Overland Middle School in Brighton, Colorado, after an antifreeze-like chemical was found in the school's potable water system. They sent nine students complaining of flu-like symptoms to an area hospital for treatment. The hospital released the students after treating them for ethylene glycol poisoning. Ethylene glycol had backflowed into the school's potable water system from the school's hot-water heating system.

During a routine maintenance check of the Overland Middle School's hot-water heating boiler, maintenance workers left open a valve on the potable water line feeding the boiler. This allowed boiler water containing the antifreeze ethylene glycol to backflow into the school's potable water system. There was no backflow preventer on the feed line to the boiler.

The Overland Middle School was closed for an additional day while workers flushed the potable water piping at the school and "repaired the hot-water heating system leak." Presumably workers installed a proper backflow preventer in the potable water line feeding the hot-water heating boiler.

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Backflow at a Premises with an Auxiliary Water System

Date of Backflow Incident: July, 1993

Location of Backflow Incident: Coos Bay, Oregon

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995.

Case History:

The occupants of a house in Coos Bay, Oregon, installed an auxiliary water system that consisted of irrigation piping supplied by water pumped from a drainage pond. The water in this pond was probably highly contaminated because it flowed from a fill area previously used for septage disposal. Eventually, the pump at the drainage pond failed. While the pump was at a repair shop, the wife noticed that the lawn needed watering, so she connected a hose from the house's potable water system to the irrigation piping. The husband returned with the repaired pump, installed it, and turned it on. The pump forced pond water through the hose connection, through the house's potable water system, and into the public water system.

Fortunately, a water meter reader was at the house at the time the water from the drainage pond was pumped into the public water system. The meter reader notified his office, and water system personnel isolated the contaminated portion of the public water system.

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Backflow at a Premises with a Reclaimed Water System

Date of Backflow Incident: September, 1996

Location of Backflow Incident: Hillsborough County, Florida

Source(s) of Information: Hillsborough County Water Department

Case History:

On September 18, 1996, a meter reader with the Hillsborough County Water Department noticed that the water meter at a home in northwest Hillborough County was registering backwards. A cross-connection had been created between the potable and reclaimed water systems at this premises, and reclaimed water was backflowing into the public potable water system.

Apparently, the County's reclaimed water service connection to this residential premises had recently been hooked up to an existing irrigation system at the premises. The irrigation system, which was previously supplied with water from the home's potable water system, was not disconnected from the home's potable water system. Furthermore, a backflow preventer was not installed at the County's potable water service connection to the premises. The County Water Department estimated that about 50,000 gallons of reclaimed water backflowed into the public potable water system.

After discovering the cross-connection, County Water Department personnel immediately shut off reclaimed water service to the residential premises where the cross-connection was found and notified the County Health Department of the cross-connection. County Water Department personnel then began flushing potable water mains in the area and advised the owner of the premises where the cross-connection was found to flush all water outlets at the premises. Based on analysis of water samples collected by its Environmental Laboratory staff, the County Water Department reckoned that the cross-connection's impact was limited to that portion of the public potable water system within 1,000 feet of the cross-connection.

On September 19, the owner of the residential premises where the cross-connection was found hired a plumber to eliminate the cross-connection.

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Backflow at a Shipyard

Date of Backflow Incident: January, 1981

Location of Backflow Incident: Norfolk, Virginia

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995. - U.S. Environmental Protection Agency, Cross-Connection Control Manual, 1989. - Watts Industries, Inc; Watts Regulator News/Stop Backflow.

Case History:

On January 29, 1981, a nationally known fast food restaurant in the city of Norfolk, Virginia, complained to the City Water Department that all their drinks were being rejected by customers because the drinks tasted salty. The City Water Department inspected all potable water lines at the restaurant for cross-connections but found none. Then the City Water Department checked with adjacent customers and received another salty water complaint from a shipyard. City Water Department personnel promptly conducted an inspection of the shipyard and discovered that sea water had backflowed into the City's potable water system.

The shipyard had a high-pressure fire protection system supplied by sea water. The sea water was delivered by both electric and diesel pumps, which were primed by using a potable water line connected directly to the high-pressure fire protection system. Workers left this priming line open. Thus, while the electric pumps were trying to maintain high pressure in the fire protection system, they were pumping sea water back through the priming line and into the City's public water system. A backflow preventer had been previously installed at the water service connection to the shipyard. However, the backflow preventer froze and burst earlier in the winter and was removed and replaced with a spool piece to maintain potable water service to the shipyard.

To correct the problem, the potable water priming line to the fire protection system pumps was removed. Also, a new backflow preventer was installed at the water service connection to the shipyard. Heat tape was wrapped around the new backflow preventer to prevent freezing of the backflow preventer.

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Backflow at a Temporary Water Loading Station

Date of Backflow Incident: November, 1976

Location of Backflow Incident: Wenatchee, Washington

Source(s) of Information: American Water Water Works Association, Opflow, May 1977 - Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995.

Case History:

In November 1976, approximately 300 gallons of liquid containing 1.2 pounds of the pesticide Endrin was backsiphoned from a pesticide applicator's truck into a small public water system serving 21 residents near Wenatchee, Washington. Endrin is a very toxic chlorinated hydrocarbon applied to orchards in late fall to control mice.

This incident occurred when, by coincidence, three applicators were filling their trucks from three separate hydrants on a water main connecting the public water system's well to a storage tank. The storage tank was about a mile away from, and about 200 feet above, the well. The withdrawal of water to fill two trucks at the lower end of the water main (near the well) created a negative pressure in the higher end of the water main (near the storage tank), and the contents of the truck at the higher end of the water main were backsiphoned into the public water system.

The public water system did not employ a full-time operator. Consequently, the contamination problem went undetected and unreported until two days after the incident. During that time, several families drank, and bathed in, the contaminated water. Fortunately, the chemical was greatly diluted in its passage through the storage tank, and therefore, no illnesses were reported.

When the State was notified of the contamination problem, it ordered the public water system to shut down, advised consumers of the situation, and initiated a sampling program. Initial samples showed 130 parts per billion of Endrin in the water.

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Backflow at a Winery

Date of Backflow Incident: December, 1970

Location of Backflow Incident: Cincinnati, Ohio

Source(s) of Information: Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition, 1995.

Case History:

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 supply 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.