A backflow preventer on a fire sprinkler service does two jobs at once. It protects the public water supply from anything sitting in the sprinkler piping, which is the water purveyor's concern, and it has to pass enough water to supply the sprinkler system's demand, which is the fire protection concern. Two sets of rules follow: the water authority's annual assembly test, and NFPA 25's annual forward-flow test. A contractor that does one and not the other leaves the owner exposed on the other side. This article covers both, who can perform them, the difference between the assembly types, and what the record has to show.
NFPA 25 requirements below follow the 2023 edition. Water purveyor requirements come from the state plumbing or safe drinking water rules and the local cross-connection control program, which vary; confirm the local program before scheduling.
The purveyor's test and the NFPA 25 test are different tests
| Test | Required by | Interval | What it proves | Who |
|---|---|---|---|---|
| Assembly test (differential pressure test) | Water purveyor, state cross-connection program | Annual in most jurisdictions, and after installation, repair, or relocation | The check valves and relief valve hold; the assembly protects the water supply | Tester certified by the state or the program (ASSE, AWWA, or state-issued) |
| Forward-flow test | NFPA 25, Chapter 13 | Annual | The assembly passes the sprinkler system's demand, including hose allowance, without excessive pressure loss | Qualified person per NFPA 25 |
| Internal inspection | NFPA 25 | Every 5 years, in addition to the annual forward-flow test | Check valves and seats are free of obstruction and corrosion | Qualified person |
The assembly test
The purveyor's test uses a differential pressure gauge on the assembly's test cocks to confirm each check valve holds against reverse flow and, on a reduced pressure zone assembly, that the relief valve opens at the required differential. The tester records the readings on the jurisdiction's form, which is often specific to the state or the water authority, and files it with the purveyor within their deadline. Assemblies that fail are repaired and retested under the purveyor's program. Whether the failure is also an NFPA 25 deficiency depends on the forward-flow result and its effect on the sprinkler system, not on the differential test alone.
The forward-flow test
NFPA 25 requires the backflow assembly on a fire protection system to be flowed once a year at the system demand, including any hose stream allowance, to prove it will not starve the sprinklers. The flow goes through a test header, a bypass, or the main drain where the piping allows it, and the technician records the inlet and outlet pressures at the demand flow. Excessive pressure loss across the assembly is a critical deficiency, and an assembly that cannot pass the system demand is an impairment, because the system behind it can no longer function as intended. Where the piping arrangement makes a full forward-flow test impossible, the standard still requires an annual test at the maximum flow achievable, with the limitation recorded. The five-year internal inspection is a separate duty and runs on its own schedule either way.
Assembly types on fire services
Double check valve assemblies (DCVA) and double check detector assemblies (DCDA) are the common choice on sprinkler services where the water in the system is not a health hazard. Reduced pressure zone assemblies (RPZ) and their detector versions (RPDA) are required where the sprinkler system contains antifreeze, foam, or other additives, or where the purveyor classifies the connection as a high hazard. The detector versions carry a small bypass meter that shows the purveyor whether water has been flowing, which matters for leak detection and for billing. The type determines the test procedure and the tester's certification, and the RPZ's relief valve discharge needs a drain that can take it, which is a frequent installation finding.
What the record has to show
Two records, one building. The purveyor's form, on its required format, filed by its deadline, with the tester's certification number. And the NFPA 25 record: the forward-flow test date, the flow achieved, the pressures, and the comparison to the system demand, kept with the rest of the sprinkler inspection records the AHJ reads. Contractors that do both keep them on the same building record and generate the purveyor's form from the same visit; Inspect Point's form library carries jurisdiction-specific backflow report formats for that reason, and the backflow trade page covers the workflow. The deficiencies and impairments article covers what a failed assembly means for the sprinkler system.
Common questions
The plumber tested the backflow; does that cover NFPA 25?
Only if the test included the forward-flow test at the sprinkler system demand and the result is recorded. The purveyor's differential test alone does not.
Does a fire sprinkler backflow tester need a license?
For the purveyor's test, yes, the certification the state or the program requires. For the NFPA 25 forward-flow test, a qualified person per the standard, which many jurisdictions read as the licensed sprinkler contractor.
What if the assembly cannot be forward-flow tested?
Record the limitation and flow what can be flowed, every year. The five-year internal inspection stays on its own schedule regardless. The AHJ decides whether the arrangement is acceptable.
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