How do you maintain a backflow preventer?
Updated August 2026
The one non-negotiable for a backflow preventer is a certified annual test, which most water utilities legally require on irrigation and fire-line assemblies and which runs $50 to $150. Beyond the test, the maintenance is winterizing the assembly so it does not freeze-crack and watching the relief port for a steady drip. This device is the barrier that keeps lawn chemicals, irrigation water, and worse from siphoning back into your drinking supply, so a failed one is a health issue, not a convenience.
| Task | Interval | Effort |
|---|---|---|
| Book a certified backflow tester | Yearly | $50–150 pro |
| File the passing test with your water utility | Yearly | 10 min · DIY |
| Task | Interval | Effort |
|---|---|---|
| Shut off, drain, and insulate the assembly | Fall | 20 min · DIY |
| Task | Interval | Effort |
|---|---|---|
| Check the relief-valve port for continuous dripping | Monthly | 2 min · DIY |
What neglect costs
Skip the annual test and two things go wrong. First, the utility can fine you or shut off service, because an untested assembly is a compliance violation in most jurisdictions. Second, and worse, a preventer that has silently failed no longer stops a cross-connection: when street pressure drops during a main break or a heavy hydrant draw, contaminated water can be sucked backward through your irrigation into the potable supply. Freeze damage is the other common failure, a cracked body or burst check that leaks and fails the next test. A rebuild kit runs $30 to $80; a full replacement is a few hundred dollars, against the $50-to-$150 test that catches wear early. See how long a backflow preventer lasts.
Leave these to a pro
The test itself must be done by a licensed, certified backflow tester with a calibrated gauge; it is not a DIY item, and the utility will not accept a self-report. Budget $50 to $150 a year, sometimes bundled with a sprinkler startup. Homeowners can and should handle the winterizing (shut off, drain, and insulate before the first freeze) and the monthly glance at the relief port. Rebuilding a failed assembly or replacing it is also pro work, generally a few hundred dollars. For what the device does and where to find yours, see what a backflow preventer is.
This whole checklist ships as reminders in OnOtto: every task above, on the right schedule for your home, snooze-proof.
Load this checklist as remindersFrequently asked questions
How often does a backflow preventer need to be tested?
Once a year in most jurisdictions, and it is usually the law rather than a suggestion for irrigation systems, fire lines, and any commercial connection. Your water utility tracks the due date and sends notices; a lapsed test can mean fines or a shutoff. Some high-hazard connections are tested more often. Keep the passing report, since the utility wants it on file. The backflow test interval page has the requirements.
Why is my backflow preventer leaking from the relief valve?
A steady drip from the relief port usually means debris is holding a check valve open or a rubber seal has worn, both of which let pressure escape. It can also spit briefly during a pressure spike, which is normal. Continuous dripping is not, and it means the assembly needs a rebuild kit or is failing its next test. Freeze damage is another common cause. Have a certified tester diagnose and rebuild it rather than guessing at parts.
Do I need to winterize my backflow preventer?
Yes, if it can freeze. Most residential backflow devices sit above ground on the irrigation line, fully exposed to the weather, and a hard freeze cracks the brass body or bursts a check valve. Before the first freeze, shut off the supply, open the test cocks and bleed valves to drain it, and wrap it in insulation. A cracked assembly means a failed test and a few hundred dollars to replace, so the twenty-minute drain is worth it.