What is Backflow and Why Should It Be Prevented?

Backflow is the reversal of flow in a potable water distribution system as a result of a pressure differential or siphon condition that exists between two piping systems. Backflow is a problem where there is a desire to keep fluids from one piping system from re-entering another piping system as in the case of a cross-connection.

A cross connection is a connection ( garden hose) or potential connection (lawn irrigation system) between any part of a potable water system and any other environment containing other substances (such as a lawn or a container of herbicide) in a manner that under any circumstances, would allow such substances to enter the potable water system.

In other words, water that goes out a faucet, sprinkler head, or emitter should never be allowed to be drawn back into the potable water system by siphon, pressure loss, or any other means.

A backflow prevention device is used to keep water that passes through it, and into the irrigation system, from coming back into the water supply. Since water in an irrigation system can be contaminated by chemicals, and other yard debris, it is considered non-potable. Very strict standards have been set and proper backflow prevention is required on all irrigation systems that Commonwealth Irrigation & Landscape install.