CROSS – CONNECTION QUESTIONS AND ANSWERS

QUESTION:  What is cross-connection?

ANSWER: A cross-connection is any temporary or permanent connection between a public water system or consumer’s potable (i.e., drinking) water system and any source or system containing non-potable water or other substances.  An example is the piping between a public water system or consumer’s potable water system and an auxiliary water system, cooling system, or irrigation system.

QUESTION:  What is backflow?

ANSWER:  Backflow is the undesirable reversal of flow of non-potable water or other substances through a cross-connection and into the piping of a public water system or consumer’s potable water system.  There are two types of backflow------backpressure backflow and back-siphonage.

QUESTION:  What is backpressure backflow?

ANSWER:  Backpressure backflow is backflow caused by a downstream pressure that is greater than the upstream pressure in a public water system or consumer’s potable water system.  Backpressure (i.e., downstream pressure that is greater than the potable water supply pressure) can result from an increase in downstream pressure, a reduction in the potable water supply pressure, or a combination of both.  Increases in downstream pressure can be created by pumps, temperature increases in boilers, etc.  Reductions in potable water supply pressure occur whenever the amount of water being used exceeds the amount of water being supplied, such as during water line flushing, fire fighting, or breaks in water mains.

QUESTION:  What is back-siphonage?

ANSWER:  Back-siphonage is backflow caused by a negative pressure (i.e., a vacuum or partial vacuum) in a Public water system or consumer’s potable water system.  The effect is similar to drinking water through a straw.  Back-siphonage can occur when there is a stoppage of water supply due to nearby fire fighting, a break in a water main, etc.

QUESTION:  Why do water suppliers need to control cross-connections and protect their public water systems against backflow?

ANSWER:  Backflow into a public water system can pollute or contaminate the water in that system (i.e., backflow into a public water system can make the water in that system unusable or unsafe to drink), and each water supplier has a responsibility to provide water that is usable and safe to drink under all foreseeable circumstances.  Furthermore, consumers generally have absolute faith that water delivered to them through a public water system is always safe to drink.  For these reasons, each water supplier must take reasonable precautions to protect its public water system against backflow.

QUESTION:  What should water suppliers do to control cross-connection and protect their public water systems against backflow?

ANSWER:  Water suppliers usually do not have the authority or capability to repeatedly inspect every consumer’s premises for cross-connections and backflow protection.  Alternatively, each water supplier should ensure that a proper backflow preventer is installed and maintained at the water service connection to each system or premises that poses a significant hazard to the public water system.  Generally, this would include the water service connection to each dedicated fire protection system or irrigation piping system and the water service connection to each of the following types of premises: (1) premises with an auxiliary or reclaimed water system; (2) industrial, medical, laboratory, marine or other facilities where objectionable substances are handled in a way that could cause pollution of contamination of the public water system; (3) premises exempt from the State Plumbing Code and premises where an internal backflow preventer required under the State Plumbing Code is not properly installed or maintained; (4) classified or restricted facilities and (5) tall buildings.  Each water supplier should also ensure that a proper backflow preventer is installed and maintained at each water loading station owned or operated by the water supplier.

QUESTION:  What is a backflow preventer?

ANSWER:  A backflow preventer is a means or mechanism to prevent backflow.  The basic means of preventing backflow is an air gap, which either eliminates a cross-connection or provides a barrier to backflow.  The basic mechanism for preventing backflow is a mechanical backflow preventer, which provides a physical barrier to backflow.  The principal types of mechanical backflow preventer are the reduced-pressure principle assembly, the pressure vacuum breaker assembly and the double check valve assembly.  A secondary type of mechanical backflow preventer is the residential dual check valve.

The Mount Pleasant water system makes every effort to ensure that our customers enjoy a continuous supply of safe drinking water.  We appreciate the help of our customers to maintain the quality of our water supply.

Cross-Connections can cause the water system to become contaminated.  A cross-connection is a link with the public water supply and a possible source of contamination.  An example of a cross-connection would be a garden hose submerged in a source of contamination such as a swimming pool, car radiator or other liquid.  If a water main break should occur or if a fire pumper used a fire hydrant while the hose was submerged in a source of contamination, the contaminant could be pulled back into the public water supply.  This occurrence, known as backflow, can be prevented.

One simple way to stop backflow is by using an air gap.  An air gap can be created by arranging your hose so that the end is at least six inches above the rim of the container it is being used to fill.  This air gap will prevent the contaminant from being siphoned into the water supply.

Another method of preventing backflow with a garden hose is using a device known as a vacuum breaker.  Vacuum breakers are inexpensive devices that can be screwed onto your outside faucet.  These devices will prevent contaminants from being siphoned back into your plumbing and the public water system.

More hazardous cross-connections or cross-connections created with permanently installed plumbing may require more sophisticated devices known as reduced pressure backflow preventers.  These devices are much more complicated and must be tested annually by certified testers.

For more information on preventing cross-connections and protecting our water supply, contact the Mount Pleasant Water System at 931-379-7717

REMEMBER: Never submerge your garden hose in anything you would not want to drink!