Tips for Air Admittance Valve Selection and Installation

Air admittance valves are helpful when you are unable to connect to an existing venting system or are simply looking to reduce roof penetrations for aesthetics

Tips for Air Admittance Valve Selection and Installation

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An air admittance valve (AAV), also referred to as a Studor vent, Studor AAV or mini vent, is a one-way mechanical valve that is installed locally at the site of a plumbing feature, allowing proper venting to occur without a connection to a larger venting system and stack vent.

There are several different AAVs on the market today that all slightly vary in design; however, they each perform the same function. 

AAVs offer various benefits for plumbers, particularly when you can’t connect to an existing venting system or are looking to reduce roof penetrations for aesthetic purposes. When installed correctly, they’re a great way to save time, money and frustration. 

Consider the following tips during your AAV selection and installation process.

Local code and manufacturer requirements

Before heading to the hardware store, be sure to check with local municipal codes and manufacturer requirements to determine if an AAV is approved for your particular application. If the use of an AAV is not permitted, the fixture or drainage system will have to be vented traditionally through the home’s existing venting system. 


You can determine which size AAV you’ll need based on the drainage fixture unit (DFU) load of the fixture(s), such as an island sink or bathroom group, that it will vent. An AAV’s ability to breathe is measured in DFUs. The higher the DFU rating on the valve, the greater amount of air that can enter the drain-waste-vent system.

DFU loads are assigned to plumbing fixtures dependent on the volume rate of discharge, the duration of operation, and the time between operations. Common fixture load ratings are shown in the table below.

To ensure proper breathing capability, determine all fixtures to be vented and calculate the total DFU load, then select the appropriate AAV for the application. Proper AAV sizing is critical because under-sizing will not allow the plumbing system to operate properly.

AAVs are typically available with 1 1/2-inch, 2-inch, 3-inch and 4-inch adapter connections. The adapter size is based on the diameter of the vent pipe it is being installed on. Generally, a vent should be sized to be half the pipe diameter of the drain it is serving (refer to local codes for specific vent size recommendations).

Pipe material

You should also verify what type of pipe material you will be connecting to the AAV adapter to ensure compatibility. In other words, AAVs with PVC adapters should only be paired with PVC pipe, and AAVs with ABS adapters with ABS pipe. This article covers more information about AAVs. 

AAV location

An AAV should be located within the maximum developed length permitted for the vent. It must be located a minimum of 4 inches above the horizontal branch drain, 6 inches above any insulation material, and within 15 degrees of vertical. AAVs cannot be permanently covered and should be installed in an area that allows air to enter the valve. They must also be accessible, should there be a need for replacement in the future.

Here are recommended supplies and installation steps.

What you'll need:

  • Safety gloves
  • Tape measure 
  • Pipe cutter or hand saw 
  • Deburring tool 
  • PVC primer, PVC cement or ABS cement
  • Thread sealant tape 


  1. Remove any protective plastic film or packaging from the AAV 
  2. Ensure AAV will be installed at least 4 inches above the horizontal branch
  3. Measure and cut pipe accordingly 
  4. Charmfer and deburr pipe 
  5. Solvent weld pipe to the provided adapter 
  6. Wrap thread sealant tape around male threads of the AAV 
  7. Insert AAV in adapter and rotate it clockwise until it is tightened securely 

About the Author

Sean Comerford is a technical customer service specialist at Oatey Co. He is a third-generation tradesman with nearly 20 years of plumbing experience, including serving as the lead plumber for commercial/residential new construction, service and fire protection jobs. He holds a State of Ohio Fire Protection License for Sprinkler and Standpipe.


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