A cross connection is any actual or potential physical connection between a public water system and any source of non-potable liquid, solid or gas that could contaminate the potable water supply by backflow.
Backflow might occur either by back-pressure or back-siphonage. Back-siphonage can be caused by high velocities in pipes from maintenance, line breaks, or fire fighting. Back-pressure occurs when the pressure at the point of use is higher than the supply pressure. Sources of back-pressure include booster pumps, boilers, elevated piping and interconnections with auxiliary systems.
Several types of backflow preventers are available:
- Air gaps (AG)
- Reduced pressure backflow assemblies (RPBA)
- Double check valve assemblies (DCVA)
- Pressure vacuum breaker assemblies (PVB)
- Atmospheric vacuum breakers (AVB)
The assembly you need is determined by the hazard. In general, we accept air gaps and reduce pressure backflow assemblies for high hazards and double check valve assemblies, pressure vacuum breaker assemblies and atmospheric vacuum breakers for low hazards. The backflow preventer chosen must be listed on the Washington State Department of Health's Approved Backflor Prevention Assembly List. Assemblies not currently listed must have been listed at the time of original installation.
We inspect assemblies upon installation and conduct periodic re-inspections on all existing assemblies. New assemblies must be annually tested by a State of Washington certified backflow assembly tester and after installation, repair, or replacement. A copy of the test report must be provided to us.
For answers to specific cross-connection control questions, lists of approved assemblies or certified testers, or to request an inspection, call (253) 502-8207 or send us an e-mail. A list of approved assemblies and certified testers are also available at our Permit Counter.
Irrigation systems, fire sprinkler systems and new or remodeled commercial or industrial installations usually require backflow prevention and A plumbing permit must also be purchased to install a backflow prevention assembly.
Plumbing permits
Within the City of Tacoma - (253) 591-5030
Outside the city limits - contact your local building official for information