How long does a backflow preventer last?

Because a backflow preventer is maintained, not just installed. Watts puts it this way in the manual for its Series 909 RPZ assemblies: "Regular checking and cleaning of the product's internal components helps assure maximum life and proper product function." The same manual warns that "Corrosive water conditions, and/or unauthorized adjustments or repair could render the product ineffective for the service intended."

The only years figure the makers give is a warranty, and it's short. The Watts manual covers defects "under normal usage for a period of one year from the date of original shipment." A warranty isn't a lifespan. It does show the maker expects the assembly to be serviced.

The moving and sealing parts. Zurn Wilkins's maintenance instructions say to "Carefully inspect rubber seal rings, diaphragms and o-rings for damage." Its repair kits guide lists the replacement parts, including the "Seal Ring," "O-Ring, Cover," "Relief Valve Diaphragm," and "Relief Valve Seal Ring."

The EPA's cross-connection manual explains why those parts matter: "Because all valves may leak as a result of wear or obstruction, the protection provided by the check valves is not considered sufficient." So assemblies are built to be tested in place. When a test shows the rubber no longer seals, it gets replaced.

A few conditions come up again and again in the makers' manuals:

• Debris in the water line. Watts says "A strainer should be installed ahead of the backflow preventer to protect all internal components from unnecessary fouling." The same manual cautions against a strainer ahead of the assembly on seldom-used emergency lines such as fire sprinkler lines, where a clogged strainer could block water when it's needed. The EPA notes that main repairs, main breaks and flushing of mains can stir up debris "within the water main that will cause fouling of backflow devices installed without the benefit of strainers."
• Pressure spikes. Zurn warns that "Damage to the device could result wherever water hammer" or thermal expansion pushes line pressure too high.
• Freezing. Zurn says "Exposure to freezing conditions will result in improper function or damage to the device." Freezes are rare in Phoenix, but an exposed assembly can still be caught by a cold night.
• Tampering. Unauthorized adjustments are one of the causes Watts lists that can make an assembly ineffective.

### What are the signs it's failing?

The clearest one on a reduced pressure zone (RPZ) assembly is water from the relief valve. Zurn says "Continuous discharge of the relief valve signifies a failure of some part of the device," and that "Most problems occur in the #1 check which is where debris enters the backflow preventer first." The EPA's test procedure points the same way: "If water exits the relief valve, in all likelihood, the first check valve is fouled." A short spit now and then is different. Zurn says "When the relief valve discharges intermittently it can be almost always assumed that the device is functioning correctly." See why an RPZ backflow preventer is spitting water.

Watts's troubleshooting table lists the same symptom, "Valve drips continually from the vent," with causes including "Fouled first check" and "Excessive back pressure, freezing, or water hammer" distorting the second check. A double check assembly has no relief valve, so it gives you no drip warning. Its failure usually shows up only on the annual test.

### How can you make one last longer?

Most of it comes down to installation and keeping it clean:

1. 1Flush the line before it goes in. Zurn's instructions say to "flush the line thoroughly to remove all debris, chips and other foreign matter" before installing.
2. 2Put a strainer ahead of it where the maker calls for one, as Watts does, but not on a seldom-used emergency line like a fire sprinkler line.
3. 3Tame pressure swings. Where spitting comes from pressure fluctuation or water hammer, Zurn says to "install water pressure reducing valves or water hammer shock arresters." See whether you need a pressure-reducing valve.
4. 4Protect it from freezing. Zurn says its assembly "may be installed outdoors only if the device is protected against freezing conditions." An insulated enclosure does that job. See whether you need a hot box for your backflow assembly.
5. 5Leave the settings alone. Only a certified tester or repairer should adjust or open it.
6. 6Keep the test on schedule. A small problem found at the annual test is a kit. A problem left for years can be a new assembly.

At least once a year, and after any repair. Phoenix enforces the 2024 International Plumbing Code with its own amendments (Ordinance G-7397), and Section 312.11.2 is one of the sections it amended. As Phoenix adopted it, the section says assemblies "shall be tested at the time of installation, immediately after repairs or relocation and at least annually," and that testing or maintenance "shall be performed by a certified backflow assembly tester or repairer in accordance with ASSE Series 5000, or otherwise approved by the Authority Having Jurisdiction." FEBCO's own manual gives the same schedule: "The assembly should be tested at the time of initial installation, after servicing or maintenance, and at least annually thereafter."

City Code 37-143, as quoted in Phoenix's backflow guidance, says "The customer shall test all backflow prevention assemblies at least once a year except that the P&D Director may require more frequent testing if warranted." If a test shows the assembly is defective, the customer must make the repairs or replacement, to the P&D Director's satisfaction, "so that the assembly is in satisfactory operating condition." Our page on commercial backflow testing requirements in Arizona covers the schedule by city, and who can test backflow assemblies in Arizona covers the tester certification.

Rebuild when the body and shutoffs are sound and the failure is in the checks or rubber. That's what repair kits are for. FEBCO's manual for its Series 860 RPZ says "The assemblies can be serviced in line, eliminating the need to remove and reinstall a unit." To service the checks, it says you can swap in new check modules or "replace the rubber components in the check modules by using the replacement rubber parts kits," and its complete rubber kit "includes all rubber parts."

Replace when:

• The body is cracked or distorted, often from freezing.
• The shutoff valves won't close or leak through, so the assembly can't be isolated or tested.
• The assembly keeps fouling right after service. Watts lists "Valve quickly and repeatedly fouls following servicing" as its own problem, caused by debris "too fine to be trapped by strainer," and its fix is a finer mesh strainer element. If fouling keeps coming back after that, replacing the assembly may be the better call.
• Parts aren't available for an old model.
• The hazard changed. A new use in the building may need a different type of assembly; see RPZ vs double check backflow.

If your assembly just failed its test, our page on what to do after a failed backflow test walks through the repair, retest and paperwork.

HQ Plumbing & Air tests, repairs and replaces domestic water backflow assemblies for businesses and homes across the Phoenix area, and we retest an assembly after we repair it. Fire sprinkler and fire line backflow is outside what we do. We're licensed and insured, with free estimates and upfront pricing. See our commercial plumbing services.

A backflow preventer lasts as long as its rubber keeps sealing. The annual test is how you find out.