What is a plumbing cheater vent?

Author: Juanita Mertz  |  Last update: Monday, March 9, 2026

Air Admittance Valves “” also called cheater valves, mechanical vents, and even durgo valves “” are mechanical devices that provide you with a one-way venting system. They allow air to enter your drain as the water disappears. Venting is an essential requirement for every plumbing system.

Are cheater vents legal?

Sometimes called "cheaters," these tubular, spring-loaded $5 vents are rated for only 1/2 DFU (drainage fixture unit), and are not allowed under most building codes.

What is the downside of the air admittance valve?

The other potential problem with using an AAV instead of a vent pipe is that if you ever get a blockage in the system that prevents the gasses from being pushed down into the sewer, those gases will have nowhere else to go.

How high does a cheater vent need to be?

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 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.

Cheater Vent For Plumbing-How It Works (AKA Air Admittance Valve)

What is the difference between an air admittance valve and a cheater vent?

Automatic air vents are spring type devices often referred to as in-line or cheater vents, while air admittance valves have no spring. Air admittance valves are more expensive and are approved in many jurisdictions where in-line and cheater vents are not because of their moving parts (springs).

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.

What happens if an air admittance valve fails?

Sometimes unwanted smells may be emitted, gargling sounds may occur or wastewater comes up from the soil pipes into the sink. All of which are signs that there may be an issue with the air admittance valve.

Where to install cheater vent?

The AAV should be located:
  1. Within the maximum developed length permitted for the vent.
  2. A minimum of 4 inches above the horizontal branch drain.
  3. 6 inches above any insulation material.
  4. Within 15 degrees of vertical.

Can you use a cheater vent on a toilet?

Yes, an air admittance valve can be used to vent a toilet.

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.

Do soil pipes need to be vented?

The soil vent pipe is essential for ensuring your home has clean, safe air. Unfortunately, we've come across homes where this was damaged, installed incorrectly, or not installed at all! Yet if it isn't working correctly, your home is at risk of being exposed to foul-smelling, potentially dangerous gasses.

Can water come out of an air admittance valve?

In order for a liquid to come out, air must come in. All DWV plumbing systems require at least one vent penetration through the roof line, which allows air to enter the system, while also permitting sewer gas to escape.

Where should the air admittance valve be located?

The short answer is a minimum of 200mm above any water entry point. So if you imagine your soil pipe run, then durgo valve / AAV must be fitted above the highest connection to the soil pipe from any sink, bath or toilet that is connected to it. Usually you'll find the installed at the very end of the soil pipe.

Does the AAV go before or after the trap?

Air admittance valves are typically placed between the P-trap of a fixture and the drain line. They're usually mounted on one leg of a sanitary tee, with the other leg going to the drain. The unit must be placed per local codes and the manufacturer's instructions.

Are trickle vents a legal requirement?

Trickle vents are required by Building Regulations when replacing windows that already have trickle vents fitted. For new window frames that are replacing old windows without vents, it must be demonstrated that ventilation will not be made worse by the installation of the new energy-efficient window.

Do air admittance valves stink?

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.

Can you have a toilet without a vent pipe?

If you have downward-sloped pipes, your toilet will most likely work without a vent. Gravity does a lot of the heavy lifting anyway. However, using the toilet without a vent means you don't have any protection against gases traveling up your drain pipes and into your home.

What is the purpose of a cheater vent?

Air Admittance Valves “” also called cheater valves, mechanical vents, and even durgo valves “” are mechanical devices that provide you with a one-way venting system. They allow air to enter your drain as the water disappears. Venting is an essential requirement for every plumbing system.

How long do air admittance valves last?

Sometimes you may find that even with an air admittance valve, there are still clogs and a sewer odor. While this is rare, it is possible. Remember that these valves should last anywhere from 20 to 30 years, so if they are only lasting for a couple of years, there may be some problems that need addressing.

How do I know if my AAV is bad?

The most accurate way to test an AAV is by using a manometer however this is not readily available. 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.

Will an air admittance valve help a slow drain?

These valves not only save space but also help keep sewer gas out of your home, promoting cleaner air. If you notice slow drains or gurgling sounds from sinks, it might mean there's negative air pressure in your drainage system, and that's the ideal time for these valves to be beneficial.

How do I know if I need an air admittance valve?

AAVs are ideal for applications such as kitchen-island sinks, remote bathrooms, and remodeling jobs. They offer cost and time savings to the homeowner and labor and material savings to the installing contractor.

Are air admittance valves to code?

Individual and branch-type air admittance valves shall conform to ASSE 1051. Stack-type air admittance valves shall conform to ASSE 1050. The valves shall be installed in accordance with the requirements of this section and the manufacturer's instructions.

Does air admittance valve need to be above sink?

Air Admittance Valve in Branch Applications (ASSE 1051)

The AAVs shall be installed after the DWV testing required by Section P2503. 5.1 or P2503. 5.2 has been performed. Individual and branch-type AAVs shall not be located not less than 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented.

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