Do you need a permit to install or replace a backflow preventer in Phoenix?

The city's technical guideline for backflow location states the rule in one sentence: "Installation, alteration or replacement of all backflow prevention assemblies requires a plumbing permit from the Planning and Development Services Department." It applies to internal assemblies required by the plumbing code (primary) and to external or secondary assemblies required by the city code. Assemblies on a fire line or fire sprinkler system need permits from both Planning and Development and the Fire Department.

The guideline also says what goes on the application. Plumbing plans show the location and size of every water service and the location, type and size of every required assembly. Site plans show the location and type of each required secondary assembly and the water service piping between the assembly and the meter. Assemblies must be certified by the USC Foundation for Cross-Connection Control and Hydraulic Research or another third party the Arizona Department of Environmental Quality approves.

Phoenix's building code amendments, carried forward into the 2024 code (effective August 1, 2025), exempt one narrow class of backflow work from the permit rule. The plumbing work that needs no permit includes: "Repair or replacement of existing 2" and smaller secondary backflow prevention assemblies. A test report, completed by a certified backflow assembly tester, shall be submitted for approval to the authority having jurisdiction at the time of installation or repair."

Read the guideline's "all assemblies" as the general rule and this item as the carve-out. It covers only the repair or replacement of an existing secondary assembly of 2 inches or smaller. A new assembly, an assembly larger than 2 inches or one on a fire line is not covered by it. If the size or type is not clear, ask Planning and Development which applies before you replace the assembly.

The Planning and Development fee schedule lists Backflow Prevention Devices under miscellaneous inspection services at $195 for the first backflow device and $98 for each additional backflow device. The plumbing permit itself is priced from the fee schedule's permit table. The schedule is Ordinance G-7465, effective January 20, 2026.

• Primary protection: backflow prevention the plumbing code requires inside the building.
• Secondary protection: the additional assembly at the service that City Code Chapter 37 requires for listed uses.
• Certified tester: a person certified to test backflow assemblies. The test report is what makes the small-assembly exemption work.

Owners and contractors on Phoenix city water who put in a new assembly, move one, or replace one. Both commercial and residential assemblies are covered, though single-family homes are generally exempt from the city's secondary rules.

• A strip mall adds a required RP at the service. This is a new assembly, so the property manager pulls a plumbing permit, shows the size and location on the plans and pays the inspection fee for the device.
• A restaurant's 3/4-inch secondary assembly fails and the plumber replaces it. It is an existing secondary assembly of 2 inches or smaller, so no permit is needed, but the certified tester's report has to reach the city at installation.
• The same restaurant's replacement is a 3-inch assembly. The answer flips: the exemption stops at 2 inches, so a permit is needed.

1. 1Measure the assembly and note whether it is primary or secondary.
2. 2If the work is exempt, hire a certified tester and submit the report at installation or repair.
3. 3If a permit is needed, apply through Planning and Development with plans showing the size, type and location.
4. 4Pay the inspection fee, $195 for the first device and $98 for each additional.
5. 5For a fire line assembly, ask the Fire Department about its own permit at the same time.

• "Replacing it in kind never needs a permit." Only existing secondary assemblies 2 inches or smaller are exempt.
• "The test replaces the permit." For the exemption the tester's report is required, and it still has to go to the city.
• "Only the city-required assemblies need a permit." The guideline covers internal plumbing-code assemblies and external city-required ones.