By in Technology

Air Admittance Valves ... Pros and Cons

AAV stands for air admittance valve.

A valve like this one is now being used to ventilate the sewer pipes in the home to allow proper air pressure to stay in the pipe traps that block sewer gasses from coming into the house through the drain of the sinks, bath tub and toilets.


The AAV is a new concept and has been used on all new constructions of home and business structures to update design and do away mainly with the vent stack pipe that once went all the way up through the roof of any and all buildings.

The vent stack pipe on our roof is about 4 inches in diameter and that now has been reduced in modern home design to about 2 inches in diameter.

Ventilation pipe

The Ventilation pipe that comes through our roof doesn't even have a cap on it to prevent squirrels from climbing down into it or to prevent tree leaves and nuts from an over grown limb of an oak tree we have to deal with by cutting back branches as much as possible.

pipe stacks that go through roof tops

The idea is to allow the removal of old style pipe stacks that go through roof tops and provide a more streamlined roof as well as serve to be attached directly under the sink or the toilet and basin of your house above the P-trap and to keep the drain pipe under everything full of water when not draining from the tank or the sink to block sewer gasses from getting inside the home and hurting the general health of everyone living in that structure.

AAV are mechanical and can fail

You need to know however that as a mechanical device, if it fails it is not likely your homeowner's insurance will cover it. You are basically at the mercy of this device or devices in your home or business. You will have to be able to tell if they begin to malfunction and know how to service them back to proper working condition.

video link provided

Here is a video link that you will like. It is simple to understand and explains why the idea of using the AAV in home or commercial buildings may not be such a bright idea. WATCH IT HERE.

Old School. DYS style

I am going to do one thing myself to remedy the squirrel and dropping acorn and leaf issue, that is, I will buy some 2 inch hardware cloth and use some wire to tie it around and over the vent pipe on our roof and leave it at that. Our house uses the old fashioned vent pipes dated as far back as the year 1945. They are mainly never covered due to the frequent possibility that they might get blocked by leaves and defeat their purpose, however, the number of acorns dropped down by mother nature will eventually require a roto-rooter to clear them out of the sewer line as they can cause plumbing problems over time.

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VinceSummers wrote on September 6, 2016, 3:51 PM

A simple correction to acorn/leaf deposition might be to cut the top of the vent pipe at, say, a 45 degree angle, instead of flat. Leaves and other detritis would have a difficult time remaining atop the pipe.

MegL wrote on September 6, 2016, 5:30 PM

Our house is 120 years or more old and the stack pipe has lasted that whole time. It has a wire mesh cover on top to stop leaves blowing down. I don't see why they would want a mechanical device to do that when the stack pipe works perfectly well, without maintenance!