Backflow is the undesirable reversal of the 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. This can render the public water supply undrinkable. Themechanism for preventing cross-connection is a backflow preventer assembly, which provides a physical barrier to backflow. The principal types of 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.

 

TERMS

• A cross-connection is any actual or potential physical connection between a drinking water system and any other non-potable substance (liquid, solid, or gas).

• Backflow occurs when water or other substances flow in the opposite direction than intended allowing contaminants to enter the public water system or consumer’s plumbing.

• A backflow incident occurs when biological, chemical, or physical contaminants enter the drinking water supply (under backflow conditions) via unprotected cross-connections. Backflow incidents may cause injury, illness, or death.

• Backflow prevention assemblies are mechanical devices installed on water service lines (or at plumbing fixtures) to prevent backflow of contaminants into drinking water through cross-connections.