A backflow assembly (also known as a backflow preventer) is mechanical plumbing equipment that is installed on your domestic plumbing service. Once installed and tested, rubber checks and springs inside of the backflow assembly will prevent any water from flowing in the reverse direction. Backflow assemblies must be tested annually.
All backflow assemblies must be both State approved, which are assemblies accepted and listed as approved by the University of Southern California Foundation for Cross Connection Research.