Short definition
In Washington, approved backflow assemblies — the RPZ on a high-hazard cross-connection, the DCVA on a fire sprinkler, the PVB on an irrigation system — must be tested annually by a certified Backflow Assembly Tester (BAT) to verify the device still prevents reverse flow. WA DOH WAC 246-290-490 sets the rule; the water utility (purveyor) enforces it.
What it is
Backflow assemblies have moving parts — check discs, springs, relief valves, air-inlet valves — that can wear, foul, or fail without obvious external symptoms. Annual testing uses a calibrated differential-pressure test gauge connected to the assembly’s test cocks (small ports built into the assembly body) to verify each component still functions to its ASSE listing.
The test sequence depends on the assembly type:
- RPZ / RPBA — four test cocks, sequence verifies both check valves and the relief valve.
- DCVA — four test cocks, sequence verifies both check valves.
- PVB — two test cocks, sequence verifies the check and the air-inlet valve.
The BAT records pass or fail and submits documentation to the water utility. Failed assemblies must be repaired (usually with a manufacturer’s rebuild kit) or replaced and re-tested.
Why it matters to a homeowner
If you have irrigation, fire sprinklers, a boiler with a make-up water connection, or any other approved backflow assembly on your property, you’ll receive an annual test letter from your water utility. Ignoring it can lead to service termination after a grace period — utilities don’t want to leave a known-untested cross-connection on the system.
Typical 2026 WA cost ranges (contractor surveys, not utility-published):
- Annual residential test for an RPZ, DCVA, or PVB: $50–$150.
- Repair kit if the test fails: $80–$250 plus labor for installation.
- Full assembly replacement: $400–$1,500 depending on size and type.
The test itself is quick — usually under 30 minutes per assembly. The BAT shows up with a calibrated gauge, connects to the test cocks, runs the test, hands you a pass/fail card, and submits documentation electronically to your utility.
When you’ll encounter this term
- Annual reminder letter from SPU, Tacoma Water, Bellevue Utilities, or whichever utility serves you.
- Newly installed irrigation system needs an initial test before activation.
- Newly installed fire sprinkler system needs an initial test plus annual ongoing.
- A backflow test fails — plumber repairs or replaces the assembly and retests.
Washington note
WA DOH WAC 246-290-490 requires that approved backflow assemblies be tested at installation, after any repair or relocation, and annually thereafter. The water utility (purveyor) is responsible for ensuring its cross-connection control program is implemented; the customer is responsible for compliance within their property — meaning the customer hires the BAT, pays for the test, and submits documentation.
WA-certified BAT testers are the only people who can run the test. The BAT certification is administered through WA DOH-approved courses and exams. High-hazard premises or assemblies with repeated failures may be required to test more frequently than annually.