A backflow prevention assembly is used to protect water supplies from contamination or pollution.
In water supply systems, water is normally maintained at a significant pressure to enable water to flow from the tap, shower etc. When pressure fails or is reduced as may happen if a water main bursts, pipes freeze or there is unexpectedly high demand on the water system, the pressure in the pipe may be reduced and may allow contaminated water from the ground, from storage of from other sources to be drawn into the system. To prevent such an occurrence, many regulaRoy regimes require there to be an air gap or mechanical backflow prevention assembly between the delivery point of mains water and local storage or use Where submerged mains inflow is permitted a backflow prevention assembly is required. In this way the backflow prevention assembly protects the potable water system from contamination hazards which can be severe. There are over 10,000 reported cases of backflow contamination each year. Some cases can be fatal.
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 each year, if relocated or repaired, and when installed.
In the United States, the Environmental Protection Agency (EPA) holds local water suppliers responsible for maintaining a certain amount of purity in potable water systems. Many states and/or local municipalities require annual testing of backflow prevention assemblies. A check valve is a common form of backflow prevention. In most cases, the law requires a double check (DC), an Reduced Pressure Principle Device(RP) device or an air gap when backflow prevention is mandated.
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 faucet) and any place where water can collect or pool.