Plumbing

Air Admittance Valves

Question: I am in the midst of adding a new bathroom and I am working on the plumbing. I need to install a vent, but I really don’t want to cut into the roof. I am considering using an air admittance valve and would like your opinion.

Answer: AAV's (air admittance valves) are not legal as vents in many jurisdictions. Check with your local building department before you install one. AAV's need to be accessible, serviceable and must be used in the highest place they can be installed. This may mean you may need to go as far as the attic to install it if you can run the vent that far. Mostly AAV's are used instead of loop venting for island sinks and bar sinks that are installed as an after thought. They are a time saver yet there are implications for installing them.

Remember you are venting sewer gases with a vent. If the AAV should fail the sewer gases from the main sewer line in the city sewer, your septic tank or cesspool can enter the living space. These gases can create an unhealthy environment. A traditional vent is the best and should be used. Sometimes this is not possible so the AAV is an alternative method for venting.

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