How to Winterize Your Irrigation Backflow Preventer

If your home has an in-ground sprinkler system, there's a brass valve assembly somewhere near where the irrigation line leaves the house — often by the foundation, sticking up out of the ground. That's your backflow preventer. Its job is to keep water from the irrigation system (which can pick up fertilizer, pesticides and soil) from flowing backward into your home's drinking water.

Because it sits above ground and stays full of water, it's one of the first things to crack when the Upstate gets its first hard freeze. A cracked backflow preventer often isn't discovered until spring, when the sprinklers are turned back on and water sprays everywhere.

How to winterize it

1. Shut off the water to the irrigation system. There's usually a dedicated shutoff valve on the irrigation line — often in the basement, crawlspace, garage or near the water meter.
2. Turn the sprinkler controller off or to its rain/off mode so it doesn't try to run with no water.
3. Open the small test cocks on the backflow preventer with a flathead screwdriver to let trapped water and pressure out.
4. Turn the ball valve handles on the backflow preventer to a half-open (45-degree) position. This lets water drain out instead of being trapped inside the valves.
5. Cover it with an insulated backflow cover or wrap, especially for long cold snaps.
6. If your system needs the lines blown out with compressed air, have a professional do it — too much air pressure can damage the system, and the backflow device can be damaged if air is pushed through it the wrong way.

In the spring

Close the test cocks, return the ball valves to their normal positions, then open the irrigation supply valve slowly to avoid a pressure surge. Watch the backflow preventer for drips or spraying before you run the sprinklers.

Signs your backflow preventer needs attention

• Water dripping or spraying from the device
• A visible crack in the brass body or a broken fitting
• Low sprinkler pressure after the system is turned back on
• Water discharging from the relief port on a reduced-pressure (RPZ) assembly

Testing requirements

Many water providers require backflow assemblies to be tested by a certified tester on a set schedule. Check with your water provider for the rules where you live. We explain how backflow devices work and why testing matters in backflow prevention and testing explained.

Protecting the rest of your plumbing from freezing matters too — see how to prevent frozen pipes in the Upstate.

Need help with your backflow preventer?

Carolina's A1 Plumbing Service installs, repairs and tests backflow preventers for homes and businesses. Learn more about our backflow prevention services. We serve Greer, Greenville, Spartanburg and the rest of the Upstate, 24/7. Call 864-365-8900.