Every drinking water system in California must have a cross connection control program, more commonly known as a backflow prevention program. Backflow prevention is designed to protect the public water supply from contamination from non-drinkable sources. Cross-connection hazards exist in a variety of places, such as factories, processing plants, laundries, dental offices and hair salons. Residential in-ground sprinkler systems are also capable of contaminating the public drinking water if they are not properly protected.
Backflow prevention devices are required on all commercial and residential properties where contamination hazards exist. These devices must be maintained and tested annually to ensure that they are working properly. The State of California requires that every backflow device be inspected annually by a certified backflow tester, and every city that operates a public water system is responsible for making sure that this is done.