Annual testing
Annual backflow testing is the recurring field test, typically once a year where a water purveyor requires it, in which a certified tester connects a differential pressure gauge to an assembly's test cocks and verifies that each check valve, relief valve or air inlet still holds. The tester tags the assembly and files a report with the purveyor; a failed assembly is repaired and retested before it is back in service.
Updated 2026 · Researched from published standards, not professional or legal advice.
Annual backflow testing at a glance
| Question | Answer |
|---|---|
| Who requires it | The water purveyor or authority, under its cross-connection control program |
| Who performs it | A certified backflow prevention assembly tester with a calibrated differential pressure gauge |
| What is tested | Each check valve, the relief valve on an RP, and the air inlet on a vacuum breaker |
| How long it takes | Minutes per assembly once the gauge is connected; the paperwork often takes longer |
| The result | A test report filed with the purveyor and a tag on the assembly showing the date and tester |
| If it fails | Repair, usually with a rebuild kit, then a full retest before the assembly passes |
Annual testing refers to the recurring field test that verifies a backflow prevention assembly still functions, performed on a cycle that is typically annual where required, set by the water authority. A certified tester connects a differential pressure gauge to the assembly's test cocks, isolates the assembly with its shutoff valves, and measures whether each check valve holds and, on a reduced pressure principle assembly, whether the relief valve opens as designed. Results are recorded and reported.
Periodic testing exists because these assemblies fail silently. Springs weaken, rubber seals wear, and debris lodges on seats, all while water service continues normally, so an assembly can look perfect from the outside and provide no protection at all. Testing is the only reliable way to know. It also creates a maintenance rhythm: a failed test leads to cleaning or repair with fresh parts, followed by a retest, which keeps the installed base of assemblies genuinely functional rather than merely present.
Property owners should treat the test cycle as their own responsibility rather than something the purveyor will chase them about, keeping records of every test and scheduling promptly when notified. Testers should follow the test procedures recognized in their jurisdiction, maintain their certification and gauge calibration, and file reports the way the local program requires. A brief water interruption during the test is normal, so owners with sensitive operations should plan the timing with their tester.
Common questions
Is annual backflow testing required?
Where a water purveyor requires containment assemblies, it almost always requires them to be tested on a recurring cycle, typically annual, and it enforces the schedule with notices and, eventually, service action. The cycle and the recognized tester credentials are set by the purveyor and the state program, so confirm locally.
What happens during an annual backflow test?
The tester shuts off the downstream valve, connects the gauge hoses to the test cocks, and runs the field test procedure for that assembly type: measuring the differential each check holds, the pressure at which an RP relief valve opens, or the point a vacuum breaker air inlet opens. Each reading is recorded against the minimum the procedure sets.
What if the backflow assembly fails the test?
It is repaired and retested. Most failures are fouled or worn check discs, springs or relief valve seats, replaced with a manufacturer rebuild kit. The retest must pass in full before the assembly is tagged and the passing report is filed.
Sources
- University of Southern California Foundation for Cross-Connection Control and Hydraulic Research, Manual of Cross-Connection Control: field test procedures for RP, double check and vacuum breaker assemblies.
- AWWA Manual M14, Backflow Prevention and Cross-Connection Control: Recommended Practices: purveyor program responsibilities and containment practice.
- ASSE International, Series 5000 Professional Qualifications Standard: the ASSE 5110 backflow prevention assembly tester requirements.
Related terms
| Differential pressure gauge | The calibrated field test instrument that measures pressure differences across the components of a backflow prevention assembly to verify they are holding. |
| Test cocks | Small valved ports on a backflow prevention assembly that give a tester gauge access to the pressure zones inside the assembly. |
| Cross-connection control program | The organized system of surveys, device requirements, testing, and recordkeeping through which a water purveyor or authority manages backflow risks. |
| Water purveyor | The utility or organization that owns, operates, and supplies a public drinking water system and is responsible for the quality of water it delivers. |
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