How often should you test a backflow preventer?
Updated July 2026
Test a backflow preventer once a year, using a licensed, certified tester, because most water utilities legally require it on irrigation systems, fire sprinklers, and other cross-connections. The annual test confirms the check valves and relief valve still hold, so contaminated water cannot be siphoned backward into the drinking supply during a pressure drop. Miss the deadline and the utility can issue fines or shut off service until you comply; the certified test itself runs $75 to $150.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Lawn irrigation system | Every year | The most common residential assembly, and the most regulated |
| Fire sprinkler line | Every year | Stagnant sprinkler water is a serious contamination risk |
| Boiler or chemical-feed connection | Every year | Any tie to non-potable water needs certified testing |
| After a repair or freeze damage | Retest before use | A rebuilt or thawed assembly must be verified before it protects the supply |
The cost of skipping it
What skipping it costs: beyond the direct hazard of lawn fertilizer, pesticide, or stagnant water siphoning into your tap, the paperwork side bites first. Utilities that mandate annual testing commonly charge $50 to $200 in non-compliance fees and can disconnect water service. A failed assembly usually needs a rebuild kit at $50 to $150 or full replacement at $300 to $800+ for larger sizes. The device also has a lifespan of its own; see how long a backflow preventer lasts.
How to do it (Certified test · $75–150)
- Find your assembly: a brass device with two test cocks and shutoff valves, near the irrigation manifold or where the fire line enters.
- Check whether your utility mailed a test notice; note the deadline and the required form.
- Hire a state-certified backflow tester (your utility keeps a list); the visit takes 20–30 minutes.
- The tester attaches a gauge to the test cocks, closes valves, and verifies each check holds pressure.
- Submit the signed report to the utility by the deadline and keep a copy with your home records.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing backflow tests schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
Why is annual backflow testing required by law?
Because a cross-connection can reverse. When city water pressure drops, from a main break, hydrant use, or firefighting, water can flow backward and pull whatever is on the other side of your irrigation or fire line into the public supply: fertilizer, pesticide, or stagnant water full of bacteria. Local plumbing codes require an annual certified test to prove the assembly still blocks that path. It is a public-health rule, which is why utilities enforce it with fines and shutoffs. Learn what a backflow preventer is and where yours sits.
Can I test my own backflow preventer?
You can inspect it, but you cannot certify it. The legal test requires a calibrated differential gauge and a licensed tester whose certification the utility recognizes, and only that signed report satisfies the requirement. You can and should do a visual check between tests: look for leaks at the relief valve, corrosion, or a device that dumps water continuously, all signs it needs service. But the annual compliance test belongs to a certified pro at $75 to $150.
What makes a backflow preventer fail the test?
The internal check valves and the relief valve wear out. Grit, mineral scale, and debris keep a check from seating fully, so it no longer holds pressure in one direction. Freeze damage cracks the body or bonnet. Rubber seats and springs simply age. A failed test usually means a rebuild kit of $50 to $150 or, on an old or frozen unit, full replacement. Testing yearly catches a marginal valve before it fails open and quietly removes your protection.