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KENTREL Corporation
Providing Professional
Services To America's Water Industry
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HISTORY OF BACKFLOW CONTAMINATION CASES
The
purpose of this page is to provide an understanding of how far-reaching
and critical backflow contamination problems are today. We have provided
actual case histories of selected backflow incidents (true accounts of
hazardous, even fatal situations with ineffective backflow prevention
techniques) compiled by the Florida Department of Environmental
Protection. These case histories are credited to
Les
O'Brien, Sr. Training Specialist at the University of Florida, TREEO
Center. He also maintains the website for the
American Backflow
Prevention Association.
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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.
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.
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.
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.
Date of Backflow Incident: November, 1993
Location of Backflow Incident: Wilson, North Carolina
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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