What backflow is
Backflow is water flowing the wrong way, from a private system back into the public water supply. A pressure drop in the main can pull water from sprinklers or equipment back toward the street.
What the device does
A backflow preventer is a set of check valves that only let water flow one way.
What happens during a test
A tester connects gauges to the device's test ports and checks that each valve holds as it should. The results are sent to the water provider.
- Gauges connected
- Each check tested
- Results recorded
- Report submitted
If it fails
Most failures are worn seals or springs that can be replaced. The device is retested after repair.
Types of devices
Homes with irrigation usually have a pressure vacuum breaker or a double check valve assembly. Businesses with higher-hazard connections, such as restaurants or medical offices, may need a reduced pressure zone assembly. Each type has its own test procedure, and the test results list the device type, size and serial number.
Your water provider decides which type is required for each connection.
Protecting devices in winter
Backflow devices that sit above ground on irrigation lines can freeze and crack. Many owners drain them in the fall or cover them with an insulated bag. A cracked device has to be repaired and retested before the irrigation system can be used again.
Questions readers ask
Why does my water provider require testing?
To protect the public water supply from contamination.
How long does a test take?
Usually less than half an hour for a residential device.
Sidney Treadway edits Homeowner Help for Plumbcraft Services, turning the questions our plumbers hear on calls into plain, practical articles for Upstate homeowners. About the editor