What “failed” actually means
During a test, the tester uses a calibrated differential-pressure gauge to confirm each part of the assembly does its job. Under the standard test procedures used in Washington:
- Check valves must hold tight against reverse pressure, at or above a minimum differential (commonly 1.0 psid).
- On an RP assembly, the relief valve must open at no less than 2.0 psid, and the first check must hold a higher differential than that opening point.
- On a PVB, the air inlet must open and the check must hold at the required minimums.
- The shut-off valves must close tightly enough for a valid test.
If any of those fall short, the assembly fails, even if it’s not visibly leaking.
The usual suspects
- Debris on a check seat. Sand, scale or pipe shavings, often stirred up by nearby water-main work. Frequently fixed with a cleaning.
- Worn rubber. Check discs, O-rings and diaphragms harden and crack over time. Fixed with a manufacturer repair kit.
- Weak or broken springs. Replaced as part of a rebuild.
- Freeze damage. Cracked bodies, bonnets or test cocks. Usually means replacement parts or a new assembly.
- Leaking shut-off valves. Can prevent a valid test and may need replacing.
Repair or replace?
Repair is usually the cheaper route. Most assemblies can be cleaned or rebuilt with a kit and retested on the same visit. Replacement makes more sense when:
- The body or bonnet is cracked (very common after a hard freeze)
- The model is discontinued and parts are hard to get
- It’s been rebuilt repeatedly and keeps failing
- It’s the wrong type or size for the current hazard
Retesting and reporting
After any repair, the assembly must be retested. Many purveyors want both the failed result and the passing retest on file. A good tester handles both reports for you, so there’s nothing left for you to submit.
How we handle it: we show you what failed, quote the fix before we touch anything, repair on the spot when we can, retest, and file everything with your purveyor. More about our repair service →
What about my deadline?
A failed test doesn’t usually reset your purveyor’s clock. Don’t let a failed assembly sit. If a repair needs to be scheduled, tell your tester your due date so it can be prioritized. If your purveyor has already set a shut-off date, call our emergency line at (425) 361-8886.
How to avoid failing next year
- Winterize irrigation assemblies every fall. Here’s how.
- Keep it accessible and protected: clean valve boxes and insulated covers help.
- Test on schedule, since small problems get fixed before they become big ones.
- Ask for a flush after nearby water-main work if your water was discolored.
Frequently asked questions
My assembly passed last year. Why did it fail now?
Rubber parts age, debris moves through the system and freezes happen. A pass last year only means it worked last year, which is exactly why testing is annual.
Will my water be shut off because my assembly failed?
Not simply for failing a test. Purveyors expect failures to be repaired and retested promptly. Problems start when a failed assembly is left unrepaired past the deadline.
Can any plumber repair my backflow assembly?
Repairs must be followed by a test from a certified Backflow Assembly Tester. Using a company that does both saves a trip and gets the passing report filed faster.