A backflow prevention device is used to protect water supplies from contamination or pollution due to backflow
pressure from contaminated water flowing from a building or outdoor area. In water supply systems, water is normally
maintained at a significant pressure to enable water to flow from the faucet. When pressure drops, such as when a
water main bursts, pipes freeze or unusual high demand on the water system, the pressure in the pipes may be
reduced and allow contaminated water from the ground, from storage or drains to be drawn into the potable water
supply system, thus causing cross contamination. Back pressure is another way that an undesirable contaminant
may enter the drinking water system. Sources of back pressure can be pumps in the water distribution system,
boilers, heat exchanging equipment, power washing equipment and the like.
To reduce the risk of contamination,
a backflow prevention device is fitted. A backflow prevention device is very important when chemicals are used,
in order to prevent chemical contamination.To prevent contamination due to back pressure, some cities and water
agencies require that an air gap or mechanical backflow prevention device be paced between the delivery point of
mains water and local storage for use. Where submerged mains inflow is permitted a backflow prevention assembly is
required, which protects the potable water system from contamination hazards. These hazards can be severe in some
cases. In many countries where regulations allow for the possibility of backflow, approved backflow prevention
assemblies are required by law and must be installed in accordance with plumbing or building codes.
A typical backflow assembly has test cocks and shut-off valves and must be tested when installed, if relocated
or repaired, and also each year. A check valve is a common form of backflow prevention. In most cases, the law
requires a double check (DC), a Reduced Pressure Principle Device (RP) device or an air gap when backflow prevention is mandated.
The United States holds local water suppliers responsible for maintaining a certain amount of purity in potable
water systems. Most of our local municipalities require annual testing of backflow prevention assemblies. The simplest, and most effective way to provide backflow prevention is to provide an air gap. An air gap is simply a space between any device that opens to a plumbing system, like a valve or a faucet, and any place where water can collect or pool.
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