Short installation instructions for the V-200 air admittance valve Air Admittance Valve / Studor Vent® Installation

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Air admittance valves or Studor Vents:

What is an air admittance valve (AAV) or Studor Vent® and how are they used? Air admittance valves or Studor Vents (a trade name for a specific air admittance valve brand) are often found where it is difficult or even impossible to install conventional plumbing vent piping; in other installations air admittance valves may supplement the building's existing vent piping system to avoid trip siphonage and dangerous methane gas leaks during periods of heavy water usage.

This article series defines plumbing vent system terms, distances, and functions, and other specifications and code requirements. We explain how plumbing vents work on buildings, why plumbing vent piping is needed, and what happens to the building drains when the vent piping is not working.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Air Admittance Valves & Studor Vents: Plumbing Vents to Prevent Trap Siphonage & Methane Gas Hazards in Buildings

Studor Redi-Vent Air admittance valve studor valve IPS CorporationDefinition of Air Admittance Valve (AAV): An AAV is a one-way valve that allows air to enter the drain to satisfy the vacuum caused by water passing down the drainage system, but that prevents sewer gases from backing up through the vent into the building.

[Click to enlarge any image]

Above, a Studor® Redi-Vent Air Admittance Valve from IPC Corporation.

Here we define Air Admittance Valves (AAVs) and explain where and how they are used.

Question: what are those one-way vents called - used under sinks in cabinets?

(Nov 8, 2012) Jon said:

What are the one way vents called under sinks in cabinets?

Reply: air admittance valves or AAVs, or "Studor Vent"

Vacuum breaker vents or "cheater vents" or "studor vetns" or more formally and properly, "air admittance valves" (AAVs) for which an example is the V-200 Jon. That's what you are asking about.

While the term "studor vent" is widely applied to describe an air admittance valve, Studor Mini-Vents as well as Redi-Vents are products of Studor Inc. & the IPS Corporation and are a brand name.

Other examples of air admittance valves (AAV s) or inline vents include models produced Keeney Mfg. Vanity Installation Kit, and the Oatey 20 DFU Sure-Vent (Oatey 39016 or 39017 and other models). Most of the AAV manufacturers offer a range of AAV models.

The Oatey SUre-Vent 39016 includes ANSI ASSE certifications stamped right on the valve top.

Standard plumbing vents vs. air admittance valves:

Standard plumbing vent (C) Daniel Friedman

Above: a conventional plumbing vent stack termination above the roof line.

If a plumbing drain is not vented to the atmosphere drain performance is likely be slow and noisy. Worse, the vacuum created by water passing through the drain waste piping system can cause water to be siphoned out of plumbing fixtrure traps. The loss of that trap water will in turn permit potentially explosive sewer gases to enter the building.

Standard Plumbing Vents

Typical "standard" plumbing systems include a plumbing vent pipe that passes up through the building roof and terminates above it.

Air Admittance Valves

Where a conventional plumbing vent system is not available or not feasible the local plumbing inspector may permit an air admittance valve to be installed.

An air admittance valve is designed to allow air in to the drain piping system to which it is connected whenever pressure in the drain system is below atmospheric pressure outside the valve.

Air admittance valve studor valve (C) Daniel Friedman

[Click to enlarge any image] Shown above: V-200 air admittance valve

Air admittance valves (AAVs) also have to withstand the positive pressure that can occur in some public sewer systems, in forced-main public or private sewer or septic systems, in plumbing drain systems using a sewage ejector pump, or in a blocked private septic system or in systems located in hilly terrain. Where high sewer gas pressures are anticipated, the sewer piping system should include a vent to the building exterior. (Studor 2016)

Short installation instructions for the V-200 air admittance valve

Some plumbing literature describes AAVs as P.A.P.A. devices. And some suppliers (National Builders Supply) recommend locating AAVs or PAPA devices throughout the plumbing system to improve drain performance by handling variations in air pressure in the drain-waste-vent system (DWV system), and to avoid trap siphonage.

Watch out: If you smell sewer gases in your building conditions could be dangerous (risking a methane gas explosion) or unsanitary. See REMEDIES for SEWER ODORS, PLUMBING and


Air Admittance Valves retail for prices between about $6.00 and $32.00 U.S.D. Below is a mechanical air admittance vent from Keeney and retailing about $6. You'll note that it looks a bit like the V-200 shown above.

Keeney air admittance valve

Air Admittance Valve / Studor® Vent Sizing

Air admittance valves (AAVs) or if you're using the "Kleenex" form of the term, Studor Vents are sold in various sizes or venting capacities. Air admittance valve capacity is the measure of the volume of wastewater and its flow rate that the valve can handle while preventing trap siphonage and methane gas hazards.

If building wastewater flows exceed the rating of the AAV then it is inadequate and the building may be unsafe as water may siphon from traps and explosive methane gas could enter the building. AAV manufacturers such as Studor® typically describe air admittance valve sizing or AAVs used in a combination of installation points to match building size: a rough estimate of the actual drain flow.

Oatey rates their AAVs in DFUs and provide four AAVS at sizes of 5, 20, 160 and 500 DFUs while some other manufacturers such as Studor describe products in flow rates of wastewater in liters per second.

See PLUMBING DRAIN FIXTURE UNITS DFUs for an explanation of plumbing vent Drain Fixture Units or DFUs, and for an explanation of how DFUs are calculated and used in sizing drain waste vent piping including the selection of a proper air admittance valve or AAV sizing.

Example AAV Size Ratings in DFUs or in Liters/Second

Air Admittance Valve Codes & Standards

Excerpts from IPC Chapter 9, Vents, on Air Admittance Valve Codes

Air admittance valve  inline vent in crawl areas must be moved up to below the kitchen sink (C) MeganThe photo of an inline plumbing vent or air admittance valve shown here, contributed by reader Megan, was posted originally at PLUMBING VENT CODES & DEFINITIONS.

This vent, installed in a basement or crawl space, was not properly-located according to Megan's plumbing inspector.

Section 917 Air Admittance Valves

917.1 General. Vent systems utilizing air admittance valves shall comply with this section.

Stack-type air admittance valves shall conform to ASSE 1050. Individual and branch-type air admittance valves shall conform to ASSE 1051.

917.2 Installation. The valves shall be installed in accordance with the requirements of this section and the manufacturer’s installation instructions. Air admittance valves shall be installed after the DWV testing required by Section 312.2 or 312.3 has been performed.

917.3 Where permitted. Individual, branch and circuit vents shall be permitted to terminate with a connection to an individual or branch-type air admittance valve.

Stack vents and vent stacks shall be permitted to terminate to stack-type air admittance valves.

Individual and branch-type air admittance valves shall vent only fixtures that are on the same floor level and connect to a horizontal branch drain.

The horizontal branch drain having individual and branch-type air admittance valves shall conform to Section 917.3.1 or 917.3.2. Stack-type air admittance valves shall conform to Section 917.3.3.

917.3.1 Location of branch. The horizontal branch drain shall connect to the drainage stack or building drain a maximum of four branch intervals from the top of the stack.

917.3.2 Relief vent. Where the horizontal branch is located more than four branch intervals from the top of the stack, the horizontal branch shall be provided with a relief vent that shall connect to a vent stack or stack vent, or extend outdoors to the open air.

The relief vent shall connect to the horizontal branch drain between the stack and the most downstream fixture drain connected to the horizontal branch drain.

The relief vent shall be sized in accordance with Section 916.2 and installed in accordance with Section 905. The relief vent shall be permitted to serve as the vent for other fixtures.

917.3.3 Stack. Stack-type air admittance valves shall not serve as the vent terminal for vent stacks or stack vents 

917.4 Location. Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented.

Stack-type air admittance valves shall be located not less than 6 inches (152 mm) above the flood level rim of the highest fixture being vented. The air admittance valve shall be located within the maximum developed length permitted for the vent.

The air admittance valve shall be installed a minimum of 6 inches (152 mm) above insulation materials.

917.5 Access and ventilation. Access shall be provided to all air admittance valves. The valve shall be located within a ventilated space that allows air to enter the valve.

917.6 Size. The air admittance valve shall be rated in accordance with the standard for the size of the vent to which the valve is connected.

917.7 Vent required. Within each plumbing system, a minimumof one stack vent or vent stack shall extend outdoors to the open air. 917.8 Prohibited installations.

Air admittance valves shall not be installed in nonneutralized special waste systems as described in Chapter 8.

Valves shall not be located in spaces utilized as supply or return air plenums. 


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