A backflow assembly is a safety device, and like any safety device it has to be verified. Here is how a certified backflow test works, why it's done annually, and what the certification means.
Written bySteven Lockhart·Reviewed byMiguel Lopez, Owner & Licensed Plumber (CSLB #974600)·Last reviewedJune 2026 · 4 min read
Quick Answer
Backflow testing works by having a certified tester connect gauges to the assembly’s test ports and check that its internal check valves and relief valve hold and operate correctly — proving water can only flow one way. It is typically required annually by the local water purveyor, the test must be done by a certified tester, and the results are documented and filed. This is part of our complete guide to backflow testing for West Los Angeles businesses.
The backflow test process is methodical. A certified tester isolates the assembly, attaches a calibrated test kit to its test cocks (ports), and measures the performance of each internal component — the check valves and, on a reduced-pressure assembly, the relief valve. The tester confirms the checks hold tight against reverse flow and that the relief valve opens at the correct pressure. If everything performs, the assembly passes; if not, it needs repair and a retest. This guide is part of our complete resource on backflow testing for West Los Angeles businesses.
Backflow testing is the verification, by a certified tester using calibrated gauges, that a backflow preventer’s valves hold and operate correctly so water can only flow one way — protecting the potable supply.
Annual backflow testing is the norm, and the backflow test requirements come from your local water purveyor under state cross-connection control rules. The table summarizes what a compliant test involves.
| Element | What it involves | Why |
|---|---|---|
| Frequency | Typically annual | Verifies ongoing protection |
| Who | Certified tester | Required for valid results |
| Equipment | Calibrated test kit | Accurate measurement |
| Outcome | Pass, or repair + retest | Failed device = no protection |
| Records | Results filed with purveyor | Proves compliance |
Backflow certification explained simply: backflow assemblies must be tested by a tester who holds a recognized backflow-tester certification, because the test requires specific training and calibrated equipment to be valid. The certification is what makes the test results acceptable to the water purveyor. When we test your assembly, the work is done by a certified tester and the documented results are filed, so your “certification” — the proof your assembly passed — is on record. We track your test date so you stay ahead of the annual deadline.
A business receives a notice that its annual backflow test is due, with a filing deadline.
New Pro’s certified tester tests the assembly, finds it passing, and files the results with the water purveyor before the deadline.
The business stays compliant with zero hassle, and New Pro flags next year’s test date so it never lapses.
The Bottom Line
Backflow testing verifies that the assembly protecting your water supply still works — a certified tester checks the valves with calibrated gauges, typically once a year, and files the results. A failed device gets repaired and retested. We handle the test, the repair if needed, and the filing. Call any time. More on our backflow testing page.
A certified tester connects calibrated gauges to the assembly’s test ports and checks that its internal check valves and relief valve hold and operate correctly, proving water can only flow one way. If it passes, the results are filed; if not, it needs repair and a retest.
Typically once a year, though the exact frequency is set by your local water purveyor under state cross-connection control rules. We confirm the requirement for your specific address and track your test date.
A certified backflow tester — the test requires specific training and calibrated equipment for the results to be valid and accepted by the water purveyor. We use certified testers and file the documented results.
It needs repair (often rebuilding the worn internal parts) and a retest to confirm it passes. A failed device means the cross-connection is unprotected, so it should be addressed promptly. We can repair and retest.
It refers both to the tester’s certification (the credential that makes the test valid) and to the documented proof that your assembly passed. The passing results are filed with the water purveyor as your record of compliance.
Yes — we document the test and file the results with your water purveyor to keep the property compliant, and we track your next test date so the annual requirement never lapses.
Written by the New Pro Plumbing content team and reviewed for technical accuracy by Miguel Lopez, owner and California-licensed plumber (CSLB #974600). Pipe lifespans are presented as typical ranges, not guarantees, and any pricing is confirmed in writing before work begins.
What's new: June 2026 — first publication.
Our certified testers handle your annual backflow test and file the results — fast and compliant. Call any time.
