A backflow preventer is a valve that stops contaminated water from flowing backward into your home's drinking water supply. It is required by code for irrigation systems and some other plumbing fixtures. Installation costs $100 to $300 depending on the type and complexity.
Without a backflow preventer, fertilizers, pesticides, and bacteria from your irrigation system could be siphoned into your home's potable water lines. Annual testing is required in most Texas municipalities.
What a Backflow Preventer Does
A backflow preventer uses a check valve or reduced pressure zone assembly to ensure water flows in only one direction. It is installed on the main water line or on a branch line serving the irrigation system. When a pressure drop occurs, the valve closes automatically to prevent back-siphonage of contaminated water.
Code Requirements in San Antonio
San Antonio and Bexar County require backflow prevention devices on all irrigation systems. The device must be installed by a licensed plumber and tested upon installation. Annual testing by a certified backflow tester is required, and test reports must be submitted to the local water authority.
Installation Cost
A simple atmospheric vacuum breaker for a single hose bib costs $10 to $30 and can be installed by the homeowner. A pressure vacuum breaker for an irrigation system costs $50 to $150 for the device, plus $100 to $200 for professional installation. A reduced pressure zone assembly costs $200 to $500 installed.
Annual Testing
Backflow preventers must be tested annually by a state-certified backflow tester. The test involves checking the pressure differential across the valve and verifying the check valves hold properly. Testing costs $50 to $100. Keep your test records for at least 3 years for compliance purposes.
