Are air admittance valves allowed in Arizona?

Phoenix adopted its current codes by Ordinance G-7397, effective August 1, 2025. For plumbing, the city's administrative code says "The provisions of the Uniform Plumbing Code or International Plumbing Code, as amended, shall apply to the installation, alteration, repair and replacement of plumbing systems." Both the 2024 IPC and the 2024 UPC are on the city's adopted list, and the designer picks one.

Other Valley cities don't all match. They adopt their own editions and amendments, so verify the current requirements for the address rather than carrying Phoenix's rule into another jurisdiction. Our Phoenix code adoption page shows how that comparison works.

Section 918 of the 2024 IPC, as Phoenix enforces it, says "Individual, branch and circuit vents shall be permitted to terminate with a connection to an individual or branch-type air admittance valve." Phoenix's published amendments to the 2024 IPC change sections in other chapters, but none in Chapter 9, so Section 918 applies as written.

The rules that come with it:

• Listed valves only. Individual and branch valves must conform to ASSE 1051. Stack-type valves must conform to ASSE 1050.
• Install after the test. The valve goes in after the drain, waste and vent pressure test is done.
• Same floor, horizontal branch. An individual or branch valve can vent only fixtures on the same floor level that connect to a horizontal branch drain.
• Height. The valve sits not less than 4 inches above the horizontal branch or fixture drain it vents, and not less than 6 inches above insulation. A stack-type valve sits not less than 6 inches above the flood level rim of the highest fixture it vents.
• Access and air. You need access to the valve, and it has to sit where air can get to it.
• One real vent outdoors. The code says "not less than one stack vent or vent stack shall extend outdoors to the open air" within each plumbing system.
• Places it can't go. Not in spaces used as supply or return air plenums. Not on sumps or tanks unless an engineer designed the vent system. Not on a vent terminal just to shrink the clearance to an air intake.

That last group is where remodels go wrong. An island sink is a common candidate because it's hard to run a vent pipe through open floor. An AAV can work there, but it still has to meet every item above.

The 2024 UPC has no air admittance valve section, and Phoenix's UPC amendments don't add one. That was a deliberate call by the UPC's own committee. In the cycle that produced the current UPC, a proposal to add AAV rules was rejected, and the committee's statement reads: "These systems use mechanical devices and there is a concern that they can and do fail." One member who voted against the rejection wrote that "we have to apply for an AMC to use air admittance valves." An AMC is an alternate materials and methods request. A proposal for the next edition describes the valve as "proposed for inclusion in the plumbing code," so the gap is known and still open.

What that means for you: if the plans follow the UPC, an AAV needs the city's approval as an alternate method before you count on it. Ask the plans examiner first. Don't buy the valve and hope.

1. 1Find out which plumbing code and edition your city applies to the job.
2. 2Read your city's amendment list for the vent chapter.
3. 3Ask plan review, in writing if you can, whether an AAV is accepted for your fixture.
4. 4Keep a real vent to the outdoors for the system, whatever else you use.

If you're adding a bathroom or moving a sink, we can help plan a venting method for review before anyone opens a wall. The local authority determines acceptance. HQ gives free estimates and upfront pricing, and we're licensed and insured. For how the device works, see what is an air admittance valve. For the traditional route, see how high a plumbing vent has to be above the roof.