What are the rules for air admittance valves?

Author: Hassie Waters  |  Last update: Tuesday, September 9, 2025

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. Individual and branch air admittance valves shall be located not less than 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented.

What is the minimum height for AAV?

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

What are the rules for installing an AAV?

AAV location

It must be located a minimum of 4” above the horizontal branch drain, 6” 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.

What is the downside to an air admittance valve?

The main problem with using an Air Admittance Valve instead of a Soil Vent Pipe, as discussed earlier, is that by preventing the gases from escaping through the top of the soil stack you are causing them to be forced down into the main drains and sewer system instead.

In what states are air admittance valves legal?

They are not illegal in California as a state because California Plumbing Code allows "Engineered Vent Systems" see Section 911.0.

Air admittance valves for plumbing venting explained, [just over 4 minutes]

What are the restrictions for 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. Individual and branch air admittance valves shall be located not less than 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented.

Why is studor vent illegal?

The Studor vent lets that air to be sucked in the pipe during water flow but doesn't let sewer gas escape out. Code is the thing that determines pipe size and also water flow. Hence no studor vents are permitted to toilets because more air is required to keep water flow going with more waste added to the toilet.

What is the life expectancy of an air admittance valve?

Air admittance valves have a typical life expectancy of 20-30 years, so if you start to have issues with sewer gases or smells being released around your sink or in the attic-wherever installed- the air admittance valve could be faulty or failed and should be replaced as soon as possible.

Does an air admittance valve stop smells?

Air admittance valves often feature rubber seals, to help create a complete seal, increasing the effectiveness of the valve and preventing any odours from escaping through small gaps.

What happens if a soil pipe is not vented?

Foul Odours and Health Concerns

If a soil vent pipe becomes blocked or damaged, foul odours from trapped gases can infiltrate living spaces.

How many fixtures can an AAV vent?

AAVs can vent more than one fixture, but their capacity must be matched to the total DFUs on the branch line they vent. AAVs range in capacity from 6 to 500 DFUs. To vent a clothes washer with an AAV, I run a 1 1/2-inch pipe up from a tee located about 4 inches behind the 2-inch trap, terminating it in the washer box.

What are the limits of AAV?

AAV vector genomes are been limited to 4.7 kb in length in order to balance the need for larger genetic constructs and effective payload delivery. Larger constructs can be attempted to be packaged in AAV vectors, however they are unlikely to be transfected and packaged enough to deliver the intended result.

Can you vent a bathroom group with an air admittance valve?

AAVs are a great alternative if you can't connect to an existing venting system due to complex pipe routing issues or obstructions – an ideal venting solution for island sinks, remote bathroom groups, home remodels and additions that would otherwise have to be tied into a stack vent utilizing specialized venting ...

Does an air admittance valve go before or after a trap?

Air Admittance Valves (AAV) are one-way vents installed after the trap on the drain line of a fixture. They're designed to address negative air pressure in the drain system, created when a fixture is drained.

What safety level is AAV?

AAV Safety

AAV vectors are biosafety level 1, and consist of recombinant transgene sequences (e.g. marker or human genes) flanked by the AAV inverted terminal repeats.

Where to position an air admittance valve?

The valve should be placed on a soil pipe that is at least 200mm above any water entry pipe or the highest point that wastewater will normally reach in the soil pipe. This is generally at the end of a soil pipe, but can also be added inline, using a soil pipe junction.

What is the problem with the air admittance valve?

Yes, there are some occasions when a Durgo / air admittance valve failure is possible. They include a) the valve may get stuck and need lubricant to be applied, b) the valve was installed poorly or in the wrong position, or c) the waste pipe is blocked and gases aren't being pushed down properly.

Can an air admittance valve be boxed in?

Air admittance valve installation height

Usually you'll find the installed at the very end of the soil pipe. If you need to, you can install them in line using a soil pipe junction. You'd usually install the air admittance valve within the loft or it is boxed in within the property.

Can an AAV fail?

Yes. Any AAV can malfunction or not operate properly because it is a mechanical device. Signs of that the Sure-Vent is not operating as intended, are foul odors.

Where are air admittance valves not allowed?

Air admittance valves are not permitted in spaces where pressure conditions adversely affect the valve's operation. They are also not allowed in concealed wall and ceiling spaces used as plenums as part of an air distribution system that is under negative or positive pressure.

How to tell if AAV is bad?

Another way is field testing in a cup of water, Place the air admittance valve (AAV) in a cup as shown below. This creates a positive pressure which seals the membrane and allows the valve to float. If the AAV sinks then most likely the membrane has been compromised which allows air to pass through the AAV and sink.

Are cheater vents legal?

There's a reason they're called 'cheater vents'--they're CHEATS. A good licensed plumber won't let you use them. I don't see why your plumber doesn't just cut into the drain that runs under the basement floor and run a new 3" vent stack.

What height should AAV be installed?

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

What are the rules for plumbing venting?

In general, the vent should be as close as possible to the fixtures it serves. This proximity helps ensure the vent can effectively equalize air pressure and prevent sewer gas entry. However, there are some common guidelines to consider: The vent should be within 5 to 6 feet of the fixture drain it serves.

Can an air admittance valve be inside a wall?

AAVs shall be accessible, should replacement be required. Such valves shall be installed in a location that allows air to enter the valve. Locating the valve in a sink or vanity cabinet is accessible. For in wall installation, use a recess box/grill combination or access grill.

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