What backflow is
Water normally flows one way: from the main in the street, through the meter, into your property. Backflow is any reversal of that flow. It can happen when pressure in the street drops, for example during a main break or heavy firefighting draw, and water on the property side gets pulled backward. If that water came from an irrigation system with fertilizer, a fire sprinkler line, a boiler or commercial equipment, it could contaminate the drinking water supply.
A backflow preventer is a mechanical assembly of check valves designed to stop that. In California, water suppliers run cross-connection control programs, so the requirement for a device and its testing usually comes from the water utility that serves your address, not from the plumber.
Common device types
| Device | Where you might see it | Notes |
|---|---|---|
| Reduced pressure principle assembly (RP) | Commercial buildings, high-hazard connections, some irrigation | Has a relief valve that discharges water when it senses a problem |
| Double check valve assembly | Fire sprinkler lines, some lower-hazard connections | Two independent check valves in series |
| Pressure vacuum breaker (PVB) | Residential and commercial irrigation | Must be installed above the highest sprinkler head |
| Hose bib vacuum breaker | Outdoor faucets | Simple screw-on or built-in device, not usually tested |
You may have a testable device if
- You own or manage a commercial, industrial or multi-family property
- The property has a dedicated irrigation meter or system
- There is a fire sprinkler connection
- There is a brass assembly with test cocks near the meter or along the irrigation line
- You have received a testing notice from your water utility
How testing usually works
- Notice.The water utility typically sends a notice when a test is due. Check the notice for deadlines and requirements.
- Hire a certified tester.Testing is done by a certified backflow tester. Check what certification your utility accepts.
- Test.The tester connects gauges to the test cocks and checks each valve; water is briefly shut off at the device.
- Repair if it fails.Failed devices are repaired or replaced and retested.
- Report.The test results are submitted to the water utility in the way it requires.
What drives the cost
- Number of devices
- Each assembly is tested separately.
- Device type and size
- Larger commercial assemblies take more time.
- Repairs
- Rebuild kits or replacement if the device fails.
- Access
- Devices in vaults, cages or hard-to-reach spots.
Questions to ask a tester
- Are you certified for testing in my water utility's program?
- Will you submit the test report to the utility for me?
- If the device fails, can you repair it and retest the same visit?
- Is my device installed correctly for its type?
Common questions
Does a typical house need a backflow preventer?
Many houses only have hose bib vacuum breakers and irrigation devices. Testable assemblies are more common on commercial, multi-family and irrigation connections. Check with your water utility.
What happens if I ignore a testing notice?
Consequences are set by the water utility. Check the notice and contact the utility if you need more time.
Why is water dripping from my backflow device?
An RP assembly's relief valve may discharge when it senses a problem. Have a certified tester or plumber check it.
General information for North Orange County, not a quote or professional advice. In an emergency, call 911.