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The following case histories are actual
examples of what can happen when adequate backflow prevention is ignored or
fails.
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 back flowed 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 illness 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, 1987, 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 back flowed 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 not 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 later, a car wash employee flushed the toilet in the
car wash's rest room 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 resident's 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 water service to the area at 7:00 A.M. on Thursday and
initiated an investigation. Sodium hydroxide, a caustic chemical, had back
flowed 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 back
siphoned 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 prevention 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 & Backflow Prevention, Volume 11 Number 2 (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 back flowed 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 using 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 water mains in the area. After investigation, the City Water Bureau concluded that a detergent solution
at a dairy had back flowed 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 back flowed 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 this latest 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 DENTAL OFFICE
DATE OF BACKFLOW INCIDENT: November 1990
LOCATION OF BACKFLOW INCIDENT: Kansas
SOURCE'S OF INFORMATION:
- Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition,
1995
CASE HISTORY
Several residents in a community in central Kansas were experiencing air in their
water. Employees of the water department traced the source to a dental office.
An air compressor at the dental office supplied air at 80 psig to dental equipment.
The water pressure in the public water system varied from 40 to 45 psig. A solenoid valve that isolated the air
supply from the potable water system malfunctioned. Consequently, the air compressor was trying to keep 80 psig
of air in the entire public water system.
The water department required the dentist to install a reduced-pressure principle
backflow-prevention assembly at the water service connection to the dental office.
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BACKFLOW AT A FILMING LOCATION
WHERE WATER IS USED FOR SPECIAL EFFECTS
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 film company was filming at a ranch in Los Angeles, California.
In the scene that the company was filming, it was snowing. The film 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 connected 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 bibb, the pressure
in the tank forced the chemical through the ranch's potable water system into California-American's public water
system. Approximately 30 gallons of chemical solution back flowed into the 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 FILM LABORATORY
DATE OF BACKFLOW INCIDENT: October 1978
LOCATION OF BACKFLOW INCIDENT: U.S. Navy ship at sea
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
Between July 21 and 31, 1977, 544 crew members aboard a large U.S. Navy ship developed
gastrointestinal disease. The illness was characterized by the acute onset of nausea, vomiting, abdominal cramps,
and diarrhea lasting for 12 to 36 hours.
On the morning of July 28, 301 crew members from four units with the highest rate
of illness were interviewed. Of these 301 crew members, 55 had been sick within the past seven days. Interview
responses showed that sick crew members were much more likely to have drunk water while the ship was at sea.
On July 19, two days before the onset of the outbreak, a chilled drinking water
system in the forward part of the ship had been used for the first time in more than a year. Because the time relationship
seemed to implicate this water system, it was shut down on July 28. Subsequently, investigators learned that photo
developer solution had back flowed into this water system.
The chilled water system in the forward part of the ship supplied water to a 40-gallon
tank via a rubber hose. Photo developer solution was mixed in this tank and then used in automatic photo developing
machines on the ship. The rubber hose was submerged in the tank, creating an indirect cross-connection and allowing
the photo developer solution to be back siphoned into the chilled water system.
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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 portions 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 STORAGE FACILITY
DATE OF BACKFLOW INCIDENT: August 1982
LOCATION OF BACKFLOW INCIDENT: Connecticut
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 August 1982, residents in a Connecticut town reported hissing, bubbling noises
coming from washing machines, sinks, and toilets. Faucets sputtered out small streams of water mixed with gas.
Propane gas had back flowed into the town's public water system. Local firefighters and other officials asked hundreds
of residents to evacuate their homes and businesses.
The town provided water to a propane storage facility in the area. Water was furnished
to the facility for both domestic use and fire protection and entered the facility through a single eight-inch-diameter
service connection. The facility included 26 subsurface 30,000-gallon liquid propane storage tanks.
On the day of the backflow incident, workers needed to repair a storage tank at
the propane storage facility. Before repairing the tank, workers had to purge the tank of residual propane. There
are two common methods for purging liquid propane storage tanks. One method is to use an inert gas such as carbon
dioxide. The other method is to use water. The use of water is the preferred method because it is a more positive
method and will float out any sludge as well as gas vapors. Accordingly, workers attempted to purge the tank using
water in this case. They connected a hose to the tank from one of the two fire hydrants at the facility. Unfortunately,
the pressure in the propane tank was about 85 to 90 psig, while the pressure in the town's public water system
was about 65 to 70 psig. Consequently, propane gas back flowed into the town's public water system. It was estimated
that about 2,000 cubic feet of gas flowed into the water system over a period of about 20 minutes. This is enough
gas to fill approximately one mile of eight-inch-diameter water main.
Fires were reported at two houses, and fire gutted one of these houses. At another
house, a washing machine exploded. Police, propane company workers, and town water works personnel, however, limited
damage and injuries by quickly sealing off the affected area. The town flushed fire hydrants and individual building
plumbing systems and monitored for gas. The propane company promptly instituted revised propane tank purging procedures
at its storage facility.
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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
CASE HISTORY
In March 1989, propane gas back flowed into the public water system in Fordyce, Arkansas.
Explosions and subsequent fires destroyed two houses and seriously damaged a local business. Three people in separate
buildings were injured when explosions occurred after they flushed toilets. Investigation revealed that the gas
had back flowed 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 a 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 A HOSPITAL / AUTOPSY
FACILITY
DATE OF BACKFLOW INCIDENT: December 1964
LOCATION OF BACKFLOW INCIDENT: Michigan
SOURCE'S OF INFORMATION:
- Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition,
1995
CASE HISTORY
For some time, nurses at a Michigan hospital complained about rusty water coming
from a hospital drinking fountain. When maintenance personnel finally looked into the matter, they discovered it
was actually blood that the nurses were encountering at the drinking fountain. This blood had
back flowed into the
hospital's potable water system from an autopsy table.
Hospital autopsy tables have a sump to collect blood and washing from the autopsy
procedure. These tables also have a hose-spray unit for washing off organs, etc. On an autopsy table at the Michigan
hospital, there was no hook to hang up the hose-spray unit, so pathologists placed the unit in the table sump when
they were not using it. There also was no vacuum breaker in the water supply line to the hose-spay unit on this
table, and the hospital had severe backsiphonage problems. Therefore, blood and other washing from the autopsy
table were sucked into the hospital's potable water system. The drinking fountain where the nurses were encountering
the blood was about two doors from the autopsy room.
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BACKFLOW AT AN INDUSTRIAL FACILITY
WHERE A CHEMICAL IS USED IN PROCESSING A PRODUCT
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
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
nontoxic, it can cause heart and urological damage if consumed in large 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 AN INDUSTRIAL FACILITY
WITH A PROCESS WATER SYSTEM
DATE OF BACKFLOW INCIDENT: 1992
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
CASE HISTORY
In 1992, a plastics manufacturing plant in Edmonton, Alberta, telephoned the City
Water Department complaining about sudsy water in their hot and cold water lines. An investigation revealed that
plant process water had back flowed into the plant's potable water system.
To prime a process water pump at the plant, workers connected a hose between the
pump and a potable water hose bibb. A vacuum breaker was originally installed at this hose bibb when the plant
was constructed. However, workers considered the vacuum breaker to be a nuisance because it sprayed water every
time they turned on the process water pump. Therefore, they removed the vacuum breaker and connected the priming
hose directly to the hose bibb. This solved the water spraying problem but created a direct cross-connection. The
process water pump produced a pressure greater than the pressure in the City's public water system and forced process
water, containing potassium hydroxide and gasoline oil, back through the priming hose and into the plant's potable
water system.
Workers that were drinking water during the day of the backflow incident complained
about raw throats. But, fortunately, no one became seriously ill.
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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
CASE HISTORY
On October 25, 1989, staff at the 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 back flowed 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 back flowed 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 MORTUARY
DATE OF BACKFLOW INCIDENT: ?
LOCATION OF BACKFLOW INCIDENT: ?
SOURCE'S OF INFORMATION:
- U.S. Environmental Protection Agency, Cross-Connection Control Manual, 1989
CASE HISTORY
The chief plumbing inspector in a large southern city received a telephone call
advising that blood was coming from drinking fountains at a mortuary (i.e., a funeral home). Plumbing and health
inspectors went to the scene and found evidence that blood had been circulating in the potable water system within
the funeral home. They immediately ordered the funeral home cut off from the public water system at the meter.
City water and plumbing officials did not think that the water contamination problem had spread beyond the funeral
home, but they sent inspectors into the neighborhood to check for possible contamination. Investigation revealed
that blood had back flowed through a hydraulic aspirator into the potable water system at the funeral home.
The funeral home had been using a hydraulic aspirator to drain fluids from bodies
as part of the embalming process. The aspirator was directly connected to a faucet at a sink in the embalming room.
Water flow through the aspirator created suction used to draw body fluids through a needle and hose attached to
the aspirator. When funeral home personnel used the aspirator during a period of low water pressure, the potable
water system at the funeral home >became contaminated. Instead of body fluids flowing into the wastewater system,
they were drawn in the opposite direction--into the potable water system.
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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 non-potable
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 non-potable water lines in the
packing house. This cross-connection allowed wastewater 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
back flowing
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 municipal water system. The other system
was a process system supplied with 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 & Backflow Prevention, Volume 5 Number 3 (March 1988)
- 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 back flowed 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 gardens 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, the homeowners 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 at 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 back-siphonage
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 the drugs, and most of the virus vaccines used to immunize chickens
are pathogenic to humans.
Therefore, poultry farms should be considered 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 THE CONSUMER'S POTABLE WATER SYSTEM
SUPPLIES A COOLING SYSTEM
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 back flowed 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 THE CONSUMER'S POTABLE WATER SYSTEM
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 had 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 slight 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, any chlorinated compound
is 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 THE CONSUMER'S POTABLE WATER SYSTEM
SUPPLIES AN IRRIGATION PIPING SYSTEM
DATE OF BACKFLOW INCIDENT: October 1991
LOCATION OF BACKFLOW INCIDENT: Southgate,
Michigan
SOURCE'S OF INFORMATION
- Drinking Water & 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 water had back flowed 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 THE CONSUMER'S POTABLE WATER SYSTEM
SUPPLIES A SPACE HEATING HOT-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 back flowed 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 Hillsborough County was registering backwards. A cross-connection
had been created between the potable and reclaimed water systems at this premises, and reclaimed water was
back flowing
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
back flowed
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 upon 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 REFINERY
DATE OF BACKFLOW INCIDENT: May 1979
LOCATION OF BACKFLOW INCIDENT: Winnepeg, Manitoba, Canada
SOURCE'S OF INFORMATION:
- American Water Works Association, Recommended Practice for Backflow Prevention and Cross-Connection Control,
AWWA Manual M14, Second Edition, 1990
CASE HISTORY
On May 25, 1979, personnel at a local refinery in Winnepeg, Manitoba, called the
City because the drinking water at the refinery had an oily, gasoline-type odor. The City took a water sample,
and a test of this sample showed a hydrocarbon in the water. It was determined that a backflow had occurred in
the refinery's laboratory.
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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. The same water main lateral served both the restaurant and the shipyard. City Water
Department personnel promptly conducted an inspection of the shipyard and discovered that sea water had
back flowed
into the City's public 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 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 back siphoned 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 « 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 back siphoned 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. The system drained and scrubbed its storage tank and flushed
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BACKFLOW AT A TIRE RETREADING PLANT
DATE OF BACKFLOW INCIDENT: March 1988
LOCATION OF BACKFLOW INCIDENT: Eugene, Oregon
SOURCE'S OF INFORMATION:
- Pacific Northwest Section of the American Water Works Association, Summary of Backflow Incidents, Fourth Edition,
1995
CASE HISTORY
On March 31, 1988, superheated water from a boiler in a tire retreading plant in
Eugene, Oregon, back flowed into the plant's potable water system. The hot water, which contained an unidentified
boiler treatment compound, broke (i.e., melted) the two-inch-diameter PVC water service pipe to the plant and damaged
the City's water main.
An unapproved backflow device consisting of two single check valves was installed
in the potable water feed line to the boiler at the tire retreading plant. Both check valves failed. There was
no backflow preventer at the service connection to the plant.
The water utility ordered the immediate installation of a reduced-pressure principle
backflow-prevention assembly at the water service connection to the tire retreading plant.
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BACKFLOW AT A VETERINARY OFFICE
DATE OF BACKFLOW INCIDENT: June 1983
LOCATION OF BACKFLOW INCIDENT: Calgary, Alberta, Canada
SOURCE'S OF INFORMATION:
- American Water Works Association, Recommended Practice for Backflow Prevention and Cross-Connection > Control,
AWWA Manual M14, Second Edition, 1990 CASE HISTORY
CASE HISTORY
On June 23, 1983, the City of Calgary, Alberta, received complaints from several
homes about poor tasting water flowing from their taps. The City had its waterworks division collect water samples
and forward them to a laboratory for analysis. Analyses showed high plate counts in some samples and detectable
traces of Escherichia coli in one sample. As a result, the City had its water works division immediately begin
flushing water mains in the area and dispatched plumbing inspectors to find out if a cross-connection was responsible
for the detection of Eschericia coli. After water mains in the area were flushed for several hours, the City collected
new water samples. Analyses of these samples showed lower plate counts, but Escherichia coli was still detectable
in the samples. After a 32-hour investigation of premises within the area, plumbing inspectors found several cross-connections
at a veterinary office.
The City ordered the installation of backflow-prevention assemblies at the veterinary
office. Analyses of water samples collected after installation of the assemblies showed no evidence of water contamination.
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BACKFLOW AT A WASTEWATER TREATMENT
PLANT
DATE OF BACKFLOW INCIDENT: December 1983
LOCATION OF BACKFLOW INCIDENT: San Antonio, Texas
SOURCE'S OF INFORMATION:
- American Water Works Association, Recommended Practice for Backflow Prevention and Cross-Connection Control,
AWWA Manual M14, Second Edition, 1990
CASE HISTORY
In December 1983, effluent from a wastewater treatment plant in San Antonio, Texas,
back flowed into the potable water system at the plant because of maintenance activities.
Eight employees reportedly suffered gastrointestinal problems. Fortunately, a reduced-pressure
principle backflow-prevention assembly was in place at the water service connection to the plant. This assembly
contained contamination within the plant site.
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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 back flowed 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
back flowed 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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