An air admittance valve (AAV) is a one-way mechanical plumbing vent that opens under negative pressure to let air into a drain system and closes to help block sewer gas. AAVs are commonly used when a traditional vent pipe to the roof is difficult to install.
What Is an Air Admittance Valve and How Does It Work?
Air admittance valves (AAVs) are mechanical devices that provide one-way ventilation for plumbing drain-waste-vent (DWV) systems, allowing air to enter the system while preventing sewer gases from escaping. AAVs are a cost-effective, efficient alternative to traditional vent pipes, reducing the need for secondary roof penetrations and simplifying plumbing installations.
How Does an Air Admittance Valve (AAV) Work?
An air admittance valve operates on negative pressure activation. When water drains from a fixture, it creates negative pressure in the pipe. This pressure opens the AAV, allowing air to enter the system and equalize the pressure. Once the pressure is balanced, the valve closes, preventing sewer gases from entering the building. Oatey’s Sure-Vent® AAV activates at a pressure change of -0.01 psi and reseals automatically.
Why Use an Air Admittance Valve Instead of a Traditional Plumbing Vent?
AAVs offer several advantages over traditional vent pipes:
- They eliminate the need for secondary roof penetrations, reducing the risk of leaks and improving home aesthetics.
- AAVs are ideal for kitchen islands, remote bathrooms, and remodels where connecting to an existing vent is difficult.
- They save time and material costs for contractors and homeowners.
Where Should Air Admittance Valves Be Installed?
AAVs are commonly used in:
- Kitchen island sinks
- Remote or basement bathrooms
- Remodels and additions where venting to the roof is impractical
Always check local plumbing codes before installation, as at least one stack vent to the roof is typically required.
How to Select the Right Air Admittance Valve for Your Plumbing System
To choose the correct AAV, calculate the Drain Fixture Unit (DFU) load for your fixture(s). The DFU represents the total water flow expected from the fixture. Select an AAV rated for the combined DFU of all connected fixtures.
Drain Fixture Unit (DFU) Load Table
DFU values vary by plumbing code and jurisdiction. Always confirm requirements for your local code.
| Fixture Application | DFU Load |
|---|---|
| Traditional Public Bathroom Group (toilet, tub, sink) | 6 |
| Traditional Private Bathroom Group (toilet, tub, sink) | 5 |
| Public Toilet (1.6 gpf) | 4 |
| Private Toilet (1.6 gpf) | 3 |
| Washing Machine | 3 |
| Bathtub with Shower | 2 |
| Sink & Disposal | 2 |
| Dishwasher | 2 |
| Shower Stall (5.7 gpm or less) | 2 |
| Sink | 2 |
| Drinking Fountain | 0.5 |
How to Install an Air Admittance Valve: Step-by-Step Guide
Follow these steps for proper AAV installation:
- Choose the correct AAV based on your calculated DFU load.
- Install the AAV vertically (no more than a 15° angle) and ensure it is not permanently covered. Place it at least four inches above the horizontal branch drain.
- Prepare the pipe: Measure and cut PVC pipe as needed. Use Oatey® Heavy Duty Clear PVC Cement and Oatey® Purple Primer for secure, contaminant-free joints.
- Attach the AAV: Wrap thread tape on the male threads, install the adaptor, and secure the AAV.
- Test for leaks: Fill the fixture with water and check all connections.
For a detailed video tutorial, see: How to Install an Air Admittance Valve.
What Are the Code Requirements and Best Practices for Air Admittance Valves?
- AAVs do not replace the requirement for at least one stack vent that penetrates the roof.
- Always verify with your local municipality or plumbing inspector before installation.
- Ensure the AAV is accessible for inspection and not permanently concealed
Additional Tips for Air Admittance Valve Installation
- Use only approved AAVs, such as Oatey Sure-Vent.
- Do not undersize the AAV, as this can cause system malfunction.
- Maintain accessibility for future inspection or replacement.
Learn More and Get Support
For more information, visit the Oatey blog: How to Install an Air Admittance Valve or explore our full range of Oatey Air Admittance Valves.
Published on May 22, 2026
Frequently Asked Questions
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What is an air admittance valve (AAV)?
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An air admittance valve is a mechanical device that allows air to enter a plumbing system to equalize pressure, preventing sewer gases from escaping.
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Where are air admittance valves used?
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AAVs are used in locations where traditional venting is difficult, such as kitchen islands, remote bathrooms, and remodels.
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Do air admittance valves meet plumbing code requirements?
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AAVs are approved in many jurisdictions but do not replace the need for at least one stack vent. Always check local codes.
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How do I know what size AAV to use?
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Calculate the total DFU load for your fixtures and select an AAV rated for that load.
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Can I install an AAV myself?
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Many homeowners can install an AAV with basic plumbing skills, but always follow manufacturer instructions and local codes.
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