Commercial Fire Protection Insights

What Happens During a Backflow Preventer Test?

If your building’s fire sprinkler system has a backflow preventer, which most do, it needs to be tested annually in most jurisdictions. Here’s what that test actually involves.

1. Isolating the Assembly

The certified tester closes the shutoff valves on either side of the backflow prevention assembly to isolate it from the rest of the water system before testing begins.

2. Pressure Differential Testing

Using a calibrated test kit, the tester checks the pressure differential across each check valve (and the relief valve, for reduced pressure zone assemblies) to confirm each component is holding as designed.

3. Checking for Proper Seating

Each check valve is tested to confirm it seats properly and doesn’t allow reverse flow, which is the entire purpose of the assembly.

4. Documentation and Submission

Results are recorded on a standardized test report, which in most jurisdictions gets submitted to the local water utility or health department as proof of compliance.

What Happens If It Fails

A failed assembly typically needs repair (such as cleaning or replacing a check valve seat) and a re-test before the water utility will consider the connection compliant again.

See our full Backflow Prevention for Fire Sprinkler Systems guide for assembly types and requirements.

Last updated: May 13, 2026

Reviewed for accuracy under our Editorial Standards

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