A backflow preventer or check valve is a device that’s installed on your home’s water pipes to keep contaminants out of the water supply.

Water supply and distribution systems are designed with the intent of water flowing in a single direction from the supply to the consumer. However, occasionally problems arise from either the supplier or the consumer that cause water to flow in the opposite direction. This is called backflow.

A backflow device or check valve prevents contamination in the potable water supply. There are thousands of cases of backflow contaminations reported in the US each year, which can be extremely dangerous and even fatal. The Environmental Protection Agency (EPA) requires that local agencies be responsible for maintaining the purity of the water supply. As a result, most local counties or water suppliers require backflow prevention devices to be installed and tested annually.

Residential backflow preventers may be found on lawn irrigation systems, wet fire protection systems, hot water heating (boiler) systems, swimming pools, water features, etc.