What is an Air Addmittance Valve (also known as a Studor Vent)?

An air admittance valve (AAV) is a mechanical device that is used to allow air to enter the drainage system of a building when other options will not work. It is a one-way valve that allows air to enter the drainage system when negative pressure develops in the system due to the discharge of wastewater or other gases. AAVs are often used as an alternative to traditional vent pipes (known as “stack vents” or “vent stacks” depending on configuration) that extend through the roof of a building to exhaust sewer gases that buildup in the drainage systems. They are typically installed in the plumbing system where they can provide adequate ventilation to the drainage system while preventing the entry of outside air, insects, and other debris.

Air admittance valves are very commonly known by the trade name “Studor Vent”, as they were first manufactured by a company named Studor. An air admittance valve works by allowing air to enter the drainage system when negative pressure develops in the system. The valve contains a rubber diaphragm that seals the valve when the drainage system is pressurized. When negative pressure occurs in the drainage system, the diaphragm in the AAV is pulled upwards, opening the valve and allowing air to enter the system.

The AAV is typically installed at the end of a drain line or in a convenient location in the plumbing system. The valve is designed to allow air to enter the system while preventing the entry of outside air, insects, and other debris. As wastewater flows through the plumbing system, it creates negative pressure that can cause water in the traps to be siphoned out, allowing sewer gases to enter the building. The AAV allows air to enter the system to equalize the pressure and prevent the siphoning of water from the traps. This helps to prevent unpleasant odors from entering the building and can improve the overall efficiency of the drainage system.

It’s important to note that AAVs have a limited lifespan and may need to be replaced periodically. Additionally, some plumbing codes may require regular inspections and maintenance of AAVs to ensure that they are functioning properly, and AAVs are not suitable for all plumbing systems and may not be approved by local plumbing codes.


Common Places Studor Vents are Installed

Far and away the most common location that I find air admittance valves as a San Antonio home inspector are under kitchen sinks when the kitchen sink is located at an “island” or a more “open” floor plan. If you were to have an area where you did not want any walls or posts for asthetic reasons, such as many modern homes are designed, but you want to have a sink or other water feature present at a location, then you will need to install a Studor vent at this location for the drain to function properly.

Basically, any time you want to have a water fixture somewhere but there is not a good place to have have plumbing vent stack drain running up through the ceiling in the area, then an AAV is going to be the correct fitting for the job.


Are Air Admittance Valves (Studor Vents) Allowed by Plumbing Code?

The International Plumbing Code (IPC) does allow the use of air admittance valves (AAVs) as an alternative to traditional vent pipes. However, the use of AAVs must comply with certain requirements set out in the IPC. The IPC allows the use of AAVs in all types of buildings, including residential, commercial, and industrial buildings should they comply with the following requirements:

  • AAVs must be installed in accordance with the manufacturer’s installation instructions.
  • AAVs must be approved by the local plumbing authority or a recognized third-party organization.
  • AAVs must be accessible for inspection and maintenance.
  • AAVs must be installed in locations where they will not be subject to mechanical damage.
  • AAVs must not be used in certain applications, such as in systems that convey hazardous waste, in buildings that are prone to flooding, or in certain types of healthcare facilities.

It’s important to note that the IPC is a model code and is not adopted uniformly across all jurisdictions. Local plumbing codes may have additional or different requirements for the use of AAVs. It’s essential to consult with a licensed plumber or local plumbing authority to determine whether AAVs are permitted and to ensure that any installation or use of an AAV complies with all applicable codes and regulations.


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