A backflow prevention device is used to protect water supplies from contamination or pollution. Many types of backflow prevention devices also have test cocks so that they can be tested or examined to ensure that they are functioning properly.

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.

Backflow prevention protects the potable water system from minor, moderate, and severe hazards. There are over 10,000 reported cases of backflow contamination each year. Some cases can be fatal. Backflow devices are required by law where needed and must be installed in accordance with plumbing or building codes. A backflow assembly has test cocks and shut-off valves and must be tested each year, if relocated or repaired, and when installed.

In this situation, dirty water from the hillside pool will back siphon or back flow down the hosepipe and into the clean water tank. To prevent this from happening, the house's external tap should be fitted with a backflow prevention device.

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.

Partial list of some backflow prevention devices

• Air gap
• Atmospheric vacuum breaker (AVB)
• Chemigation valve (primarily used in agriculture)
• Check valve although not a legally approved method of backflow prevention.
• Double check valve, or double check valve assembly (DCVA)
• Pressure vacuum breaker assembly (PVB)
• Reduced Pressure Principle Backflow Prevention Assembly (RP), RP Assembly, or RPZ (Reduced Pressure Zone)

External links

• IAPMO
• Drinking Water & Backflow Prevention magazine
• ICC
• ASSE
• The American Backflow Prevention Association
• Foundation for Cross-Connection Control and Hydraulic Research
• Backflow Prevention TechZone
• Australian Backflow Prevention expert

All the text above is licensed under the GNU Free Documentation License. To see the full article with more information, visit the Wikipedia article "Backflow Prevention".

• What is Backflow Prevention?
• How Do Backflow Prevention Assemblies Work?
• What are Enclosures?
• What is a Backflow Device?
• Why Do I Need a Backflow Device?
• What Does a Backflow Device Look Like?
• What Do all These Plumbing Terms Mean?