What is an Air Admittance Valve?

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Venting is an essential aspect of every plumbing system. Traditionally, the plumbing drain-waste-vent system consists of drain pipes for waste removal and vent pipes to prevent the escape of unwanted gases through the dry trap and maintain the required pressure balance to facilitate water flow. The drainage system in most homes directly vents through the roof with the help of a vent pipe connected to the drain pipe.

However, connecting various plumbing fixtures to the venting system during plumbing remodel is challenging and complex. Some structural elements in a building can make it tough to place additional vent pipes on the roofline. In such situations, plumbers use an effective venting option known as an air admittance valve. 

What is an air admittance valve?

Air admittance valves (AAV), also referred to as durgo valves, present a viable alternative to venting a plumbing fixture when it is difficult or expensive to connect its drain to the existing vent network. They are simple, negative pressure-activated one-way mechanical devices installed to facilitate proper venting. They allow the pipes to drain correctly and prevent sewer gases from entering the living space by equalizing the air pressure in the pipes without connecting to the primary venting system. 

While most air admittance valves are ideal for installation inside a building, some are designed specifically for outdoor use.

Working of an air admittance valve

When the wastewater discharges inside the drain, it creates pressure that opens the air admittance valve, which lets clean air into the pipe and balances the air pressure before it closes again. It prevents the escape of foul air into the home while allowing air to enter the drain whenever required. The rubber seals in the AAVs prevent odors from escaping even through small gaps. 

AAVs are fitted in areas with good airflow and facilitate easy access if a blockage occurs. They are placed between the fixture p-trap and the drain line, mounted well above the highest water entry point. Your plumbing professional should check local codes and manufacturer’s instructions before installation.

When to install an air admittance valve?

A home plumbing system can benefit from air admittance valves if it has slow-draining toilets or noisy sinks. A plumber can fit an AAV when a homeowner does not want more roof penetrations due to design and aesthetic limitations or when it is hard to connect the fixture to an existing venting system due to obstructions and complexities. Air admittance valves offer a cost-effective venting solution for new home additions, island sinks, or far-away bathrooms.

Air admittance valves pros

  • Maintenance-free

  • Allows greater flexibility in planning plumbing fixture layout

  • Saves labor and material costs

  • Long life and easier replacement

  • Reduces roof penetrations and the possibility of potential leaks

Air admittance valve cons

  • Some local and state codes prohibit their use

  • They are susceptible to damage by rodents 

  • Like any mechanical device, AAVs can fail, allowing sewer gases inside the living area

Consult a local plumber to inspect the plumbing system and determine the feasibility of installing an air admittance valve if you suspect that the existing venting system is not working correctly.


Much Better Plumbing is the premier residential and commercial plumbing service for homeowners and businesses in the Las Vegas area. We are licensed, bonded, and insured. Call us today at 702-996-5220.

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