Backflow Prevention & Testing in Torrance

What Backflow Is & Why It Matters

Backflow is the unintended reversal of water flow in a plumbing system. Under normal conditions, water moves in one direction: from the supply into your property. When that flow reverses, contaminants from irrigation lines, boilers, fire suppression systems, or industrial equipment can enter the potable water supply.

Two mechanisms cause this. Back-siphonage occurs when a drop in supply pressure creates a vacuum, pulling water backward through the line. Backpressure occurs when downstream pressure exceeds supply pressure, forcing water in reverse. Both turn a cross-connection into a contamination path. A cross-connection is any point where a potable water system connects, actually or potentially, to a non-potable source such as an irrigation system or fire line.

California Testing Requirements & Torrance Municipal Water

California’s cross-connection control requirements are governed statewide by the State Water Resources Control Board. As of July 1, 2024, these rules are codified in the Cross-Connection Control Policy Handbook, which replaced the prior Title 17 backflow regulations. Under this framework, any backflow prevention assembly must be field tested at least once per year by a certified backflow prevention assembly tester and also after installation, repair, or relocation.

Locally, Torrance Municipal Water administers the city’s water system and oversees compliance. Failure to complete required testing or maintain adequate protection can result in discontinuation of water service. Keeping your assembly current supports continued access to service and the integrity of the broader water supply.

Common Backflow Prevention Assembly Types

The right assembly for a given connection depends on the degree of hazard present, ranging from high to lower risk:

• Air-gap separation (AG): A physical break between the water supply outlet and the receiving vessel, providing the highest level of protection by eliminating any direct connection entirely
• Reduced pressure principle assembly (RP): Contains two independent check valves and a relief valve, making it appropriate for higher-hazard connections such as commercial or industrial applications
• Double check valve assembly (DC): Two independently operating check valves in series, commonly used for lower-hazard connections
• Pressure vacuum breaker (PVB): Protects against back-siphonage and is frequently used on residential irrigation systems

Higher-hazard commercial and industrial connections generally require RP-level protection, while lower-hazard residential irrigation connections may qualify for a DC or PVB assembly. The specific requirement depends on what’s connected and how that connection is classified under California’s cross-connection control program.