Backflow preventer annual test for fire sprinkler systems — what building owners need to know

The annual backflow preventer test for a fire sprinkler system goes to your water utility, not your fire marshal — and it's a different contractor than your sprinkler company. A plain-English guide to who runs the test, who gets the report, and what happens when it fails.

Two annual obligations — one that goes to the fire marshal, one to the water utility

If your building has a fire sprinkler system, you almost certainly have a backflow preventer on the fire service line. And if you have a backflow preventer, you owe two separate reports to two separate agencies on two separate schedules.

Most property managers know about the NFPA 25 annual inspection report — the one that documents the sprinkler system's test results and goes to the fire marshal or AHJ. The backflow preventer test is the other one, and it goes to your water utility (the purveyor), not to the fire marshal. These are different filing paths, different contractors, and different timelines. Mixing them up is how you end up current with one agency and overdue with the other.

Why fire systems have backflow preventers

A fire sprinkler system is connected to the public water supply. Under normal conditions, water flows one direction — from the main into the building. But a pipe failure, pump failure, or pressure drop can reverse that flow. Without protection, water that's been sitting in a fire system for months (or longer) can get pulled back into the potable supply.

The backflow preventer stops that reversal. It's the device on the fire service riser or incoming fire service line between the public main and the building's sprinkler system. Washington State and the local water purveyor require it — and require that it be tested annually to confirm it's actually doing its job.

RPZ vs. double-check — which one is on your fire system

Two backflow preventer types are common on commercial fire systems:

Reduced Pressure Zone (RPZ) assembly. The higher-protection device. Required when the downstream risk is classified as a severe or high hazard — which most fire systems qualify as because antifreeze, non-potable water, or system chemicals may be present. An RPZ has two independently acting check valves and a differential pressure relief valve between them. If either check fails, the relief valve opens and discharges water rather than letting contaminated water flow back into the main. If you see a device on your fire service line with a side discharge that drips or flows during normal operation, that's the relief valve doing its job (or signaling a problem, depending on the flow rate).

Double Check (DC) valve assembly. A lower-protection device with two check valves and no relief port. Used on fire systems classified as low hazard in some jurisdictions. Less common than RPZ on commercial fire systems in Washington because most local water purveyors default to RPZ for fire service.

The type on your system is specified on your water utility's file for the property. Your NFPA 25 inspection report should also reference it. If you're not sure which you have, the test report from your last annual backflow test will identify it.

Who runs the test

Backflow preventer testing is a separate license from fire sprinkler contracting. In Washington, backflow assembly testers are certified through the Washington State Department of Health (DOH). A licensed Level 3 fire sprinkler contractor is not automatically certified to perform a backflow assembly test — and the water purveyor requires a DOH-certified tester, not just any licensed contractor.

Your options:

• Your NFPA 25 inspection company may also have certified backflow testers on staff. Many do. If they do, they can combine the annual NFPA 25 visit with the backflow test for efficiency.
• Some sprinkler contractors are also DOH-certified backflow testers. We can clarify our current certification status when you call.
• Specialty backflow testing companies handle only the test and report. They don't do sprinkler repairs, but they know the purveyor reporting systems.

The test itself is short — typically 30-60 minutes for a standard commercial RPZ. The tester will shut down the system briefly, isolate the device, and run the checks on both check valves and the relief valve. The system goes back in service the same visit in most cases.

Who gets the report — and how it's submitted

The annual backflow test report goes to your water purveyor, not to the fire marshal. Most utilities in our service area have moved to online submission portals. Common purveyors in our service area and their general reporting approach:

• City of Bonney Lake / Cascade Water Alliance — annual test reports submitted online through the utility's customer portal or by the tester directly.
• Pierce County Utilities — tester submits to PierceCountyWa.gov utilities portal.
• Tacoma Water — TacomaWater.org has a backflow reporting section; tester typically submits on the owner's behalf.
• Lakehaven Utility District (Federal Way area) — online portal, tester submits.

In most cases, the certified tester submits the report directly to the utility on your behalf using your account number. You should receive confirmation that it was filed and a copy of the test results. Keep that copy. If the utility asks whether you're current, you want the filed report in hand.

The fire marshal is a separate audience. They care about the NFPA 25 annual report and the system's operational status. Some AHJs in our service area will ask whether the backflow preventer is current as part of a fire inspection — if so, the purveyor's filed test report is the documentation they'll want.

What happens when the test fails

A backflow preventer test failure means one or both check valves, or the relief valve (on an RPZ), did not meet the pass criteria for differential pressure. The tester's report will note which element failed and by how much.

The tester's job ends at the written report. Repair and replacement of the backflow assembly is a licensed plumbing or fire protection contractor scope, depending on the assembly size and jurisdiction. For fire service backflow preventers, we handle the repair side.

Common repair outcomes:

• Check valve seat or disc replacement. The most common repair. The assembly comes apart, worn components are replaced with listed repair kit parts, and the device is re-tested. A test-and-repair-and-re-test on the same visit is the fastest path.
• Relief valve replacement (RPZ only). If the relief valve's differential is out of spec, the valve may need to be rebuilt or replaced.
• Full assembly replacement. When the assembly is old, corroded, or out of production (making repair parts unavailable), replacement is more cost-effective than repair. Replacement requires a permit in most jurisdictions for fire service assemblies above a certain size.
• Parallel assembly path. Some buildings have a parallel standby assembly for systems where shutdown is not acceptable. If yours does, the repair can happen with the standby assembly holding service. Confirm with the tester before assuming this path is available.

The re-test after repair is submitted to the utility the same way as the original annual test. The utility tracks both the fail result and the pass-after-repair result in the account history.

Timing and coordination with NFPA 25

The backflow test and the NFPA 25 annual inspection are separate obligations with separate cadences, but they can often be coordinated for efficiency. If your NFPA 25 inspection company has certified backflow testers, scheduling them for the same week (or even the same day) reduces the number of site visits, the number of brief system shutdowns, and the number of different vendors you're coordinating.

A few timing considerations:

• Water purveyor deadlines. Most utilities send an overdue notice after 12 months. Some flag the account and can add a surcharge or service interruption warning for chronic non-compliance. Know your purveyor's specific reminder schedule.
• Winter testing on RPZ assemblies. An RPZ that is exposed (or in an inadequately heated location) can freeze. Scheduling the annual test before winter, when a freeze-thaw failure is more likely, is smarter than scheduling in January.
• Shutdowns and occupant notification. The backflow test requires a brief shutdown of the fire service. For occupied commercial buildings, that's a brief impairment under NFPA 25. Most testers complete the RPZ test quickly enough that a fire watch is not required — but confirm with the tester and your AHJ before scheduling in a high-occupancy or high-risk setting.

What to have ready when you call

When coordinating the annual backflow test, the tester or contractor will typically need:

• The property address and the water utility account number.
• The type of assembly (RPZ or DC), the manufacturer, and the size if known — or access to the mechanical room to look.
• The prior year's test report, if available. Year-over-year comparison is meaningful for RPZ relief valve drift.
• A contact who can provide building access and brief system shutdown notification.

If the test is overdue or the utility has flagged the account, mention that when you call. We can usually sequence a test-and-repair-if-needed visit to close out the compliance gap in a single mobilization.

Last reviewed by Michael Berger, Owner · 1st Choice Fire · WA L&I #1STCHCF770OF