No. The forward flow test pushes water through the fire line backflow preventer in the normal direction to prove it opens and passes enough flow. The backflow test uses a gauge kit to prove the checks close tight against reverse flow. In Phoenix, the annual fire line test must include both, done by a Fire Marshal permitted tester.
What the forward flow test proves
The forward flow test is a fire protection test. It asks one question: when the sprinklers open, will enough water get through the backflow preventer? A check valve that sits closed for years can stick or stiffen. NFPA explains that a backflow preventer on a fire system needs inspection, testing and maintenance "(such as a forward flow test) to ensure that the backflow remains operational and does not seize up, which could impair the fire protection system."
NFPA 25 is the standard for inspecting, testing and maintaining water-based fire protection systems. NFPA's own summary of its frequencies lists the backflow preventer as an annual test item. The same summary lists a weekly inspection for reduced pressure backflow preventers, an interior inspection of the backflow preventer every five years, and a main drain test that goes "quarterly if system is supplied through a backflow or pressure reducing valve."
The test needs real water volume. McKinney, Texas, a fire marshal's office outside Arizona, describes the NFPA 13 requirement in its notice to contractors as "a forward flow test, at the system demand, to ensure proper operation of the backflow prevention assembly." It says all automatic sprinkler systems "shall provide a method to perform the forward flow test," and it accepts hose outlets on the system side of the device or a test header like a fire pump's. Valley fire departments set their own procedures, so ask yours how the flow is measured and where the water goes.
Manufacturers say the same thing in their manuals. Watts, in the manual for its 957 and 957RPDA assemblies, warns that "If installed on a fire sprinkler system, all mechanical checks, such as alarm checks and backflow preventers, should be flow tested and inspected internally in accordance with NFPA 13 and NFPA 25."
What the backflow test proves
The backflow test is a drinking water test. It asks a different question: if pressure on the fire side ever rose above the city side, or the city side dropped, would the checks hold? It's done under Arizona's state backflow rule and your city's code, not under NFPA.
Arizona's rule, R18-4-215, says each required assembly "shall be tested at least annually, or more frequently if directed by the public water system or the Department," and again "after installation, relocation, or repair." Testing follows the procedures in Section 9 of the USC Manual of Cross-Connection Control. It must be done by someone certified as a "general" tester by an approved body. Just so you know, the state rule exempts Class 1 and Class 2 fire sprinkler systems, but Valley cities still require protection and testing on those lines under their own codes.
The tools are different too. Zurn Wilkins' test instructions for its 350 and 350DA double check assemblies start with "Equipment Required: Differential pressure gauge test kit." The first step in the Zurn Wilkins procedure is "TEST NO. 1 - TIGHTNESS OF #1 CHECK VALVE." No big flow is involved. The tester closes the shutoffs, opens the test cocks in order and reads pressure differences across each check. On a detector assembly, NFPA notes the bypass is "also protected with a smaller DCVA," so there's a second, smaller assembly to test.
A pass on one test says little about the other. A check can seal perfectly and still open too stiffly under full flow. Or it can swing wide open under flow and still leak back when the pressure reverses.
| Forward flow test | Backflow test | |
|---|---|---|
| Main question | Does the fire system get enough water through the assembly? | Do the checks stop reverse flow into the city main? |
| Water direction | Normal flow, at system demand | Static, with shutoffs closed |
| Tools | Hose outlets or test header, flow measurement | Differential pressure gauge kit |
| Rule behind it | NFPA 25 for the annual test, NFPA 13 for new systems | R18-4-215 and the city backflow code |
| How often | Annually | Annually, plus after install, repair or relocation |
| Phoenix report goes to | Class 1 and 2 fire systems: Director and City Fire Marshal within 30 days | Class 1 and 2: same place, same 30 days; other lines: by the Director's due date |
Can it be one visit, and who does it?
Yes, and in Phoenix it's built that way. City Code 37-143 says that for fire lines and fire sprinkler systems with backflow assemblies, "the initial and annual test must be performed by a certified tester who is also permitted by the City Fire Marshal to test fire lines or fire sprinkler systems. The initial and annual test must include a full flow test." City Code 37-144 adds that for Class 1 and 2 fire systems, "Annual flow and valve confidence tests must be performed by a tester who is permitted by the City Fire Marshal to test or maintain fire lines or fire sprinkler systems." Results go on city-approved forms "to the Director and the City Fire Marshal within 30 days following the inspection."
So in Phoenix, one qualified fire contractor can do the flow test and the backflow test in the same visit, and the results go in together. On Class 1 and 2 fire systems they're due within 30 days; otherwise the city's general deadline is the date the Planning and Development Director sets (City Code 37-143). Both halves are fire work. A plumbing backflow tester who isn't permitted by the Fire Marshal can't do the fire line test there, even though they can test your domestic and irrigation assemblies. For more on tester rules, see who can test backflow assemblies in Arizona.
Taking a fire line out of service for testing has its own step. Phoenix's test report instructions say that "Before testing a backflow assembly on a fire sprinkler system, check with the local jurisdiction on proper procedures and notify the alarm company responsible for monitoring the fire system." If there's no alarm company, the tester notifies the Fire Department. The report records when the system went off line and when it came back.
Other Valley cities handle the paperwork their own way:
- Mesa requires every assembly to be "tested and serviced at least once each year prior to the compliance due date," by a tester on the city's recognized list (City Code 8-1-11).
- Scottsdale requires assemblies to be "tested at least once a year" (Revised Code 49-65). Older Class 1 and 2 systems without a double check must have the single check's internal parts inspected yearly using NFPA 25 procedures, with records sent to the fire department and the Water Resources Division.
- Tempe asks the user to "notify the department fifteen (15) days in advance when the annual tests are to be done," so the city can witness them (City Code 33-107).
Two quick scenarios:
A Phoenix office building gets a passing gauge test but no flow test. The report doesn't meet City Code 37-143 for a fire line, because the annual test has to include a full flow test. Have the fire contractor complete it and resubmit within the deadline.
A Tempe warehouse fails its forward flow test. The checks close fine on the gauge kit, but the system can't reach its flow. The fire contractor has to find out why. The cause may be in the assembly, a valve, or the buried supply line feeding it. If it's the underground pipe, that part is a pipe repair.
What to do after the test
Your steps, in order:
- 1Book one fire-licensed contractor for both tests. In Phoenix, confirm the Fire Marshal permit before the visit.
- 2Warn the alarm company, and expect the tester to log the time the system goes off line.
- 3Get both results on the report. A gauge pass alone isn't a complete fire line test in Phoenix.
- 4File on time. In Phoenix that's within 30 days for Class 1 and 2 fire systems, and by the Director's due date otherwise; elsewhere, by your city's due date. See where to send backflow test reports in the Phoenix area.
- 5Fix failures fast. If a test shows the assembly is defective, Phoenix requires repairs or replacement "so that the assembly is in satisfactory operating condition." Our guide to what happens after a failed backflow test covers the retest.
If the test points to the underground line, Scottsdale's code is a good reminder of who owns it: fire line owners are responsible for "maintenance and repair of that line up to the main line including the tapping sleeve and valve." For the metered bypass on many fire services, see what a double detector check assembly is, and for the base rules, commercial backflow testing requirements in Arizona.
HQ Plumbing & Air doesn't test fire line assemblies or work on sprinkler systems, but we do repair underground fire lines when a test turns up a buried leak, with free estimates.