AAV problems?

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Tampa, FL
HI all,

Been in the house for 20 years. It was built new. While I do think there is a vent stack for the master bath, the builder installed AAVs at every bathroom sink in the house. The master bath has 2 different vanities, each with a sink, a toilet, and a shower. It's been fine for years up until a few months ago when both sinks in the master bath started giving off a sewer smell ONLY when you run the water. So if you run water in the sink, you smell a little of the sewer gas. I thought the AAVs needed to be replaced, so I did, and it solved the problem for about 2 days and then the smell came back. I am not sure what the issue is. You don't smell anything unless you run the water, so I imagine it has to do with gas behind the P-trap coming out when the water runs through. Unless I installed the new valves the wrong way (which is possible I guess but unlikely as I bought the same ones from Oatey, unscrewed the old ones and screwed the new ones on), I am not sure what else I can look at to fix it. I did take both P-traps apart to clean them but it hasn't really done anything.



Well-Known Member
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Smell could be from junk trapped in the sink. Maybe try a bleach solution into the lavatory drain. Or even more powerful would be to block the tailpiece, and fill the bowl with bleach solution to the rim. Let it sit. I am not a plumber.

You would need a tub under the lav to collect the bleach solution when you unblock.

You could also sanitize the threads on the loose AAV to your satisfaction, and see if you can gently blow air from the threads below. You should not be able to.

Another test would be to tape (good enough to seal) a tube into the AAV socket, and run the tube out the window. If the smell still happens when you run water, the AAV was not the problem.


Retired Defense Industry Engineer xxx
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New England
It's not uncommon for some crud to accumulate in the overflow or above the trap in the downpipe over time.

AAVs are one-way valves...letting air in, not out, when they are working properly. AAVs cannot be the only vents in the structure...there still must be at least one vent out the roof, or up high enough outside.
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