Sewer gas from bathroom vanity

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Paul Blakely

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After 4 to 5 years trouble-free, we're now frequently smelling sewer gas from the bathroom vanity sink. The only thing I can think of is that the p-trap must be siphoning out. Is it because the 13" length from the bottom of the sink to the bottom of the p-trap is too long?

It's been 6 years since this remodel, but I'm pretty sure the dwv vent pipe on the other side of the wall properly goes down to the main drain and also to the upstairs bath and out the roof.

Would an AAV help? It looks like there would barely be enough room to install one between the trap and the wall.
 

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LLigetfa

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The only thing I can think of is that the p-trap must be siphoning out.
You can test that theory by slowly pouring a small amount of water down the drain. If it still smells then most likely there is an established bacteria colony in there. Get a long bottle brush and thoroughly clean out the pipe.
 

Reach4

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There is a good chance that you are smelling stuff that is in the sink. Spray bleach solution through the overflow holes.

If you really were smelling gas that made it through the trap, you might have a reversible trap. That would let you have a 4 inch water seal, instead of a 2 inch water seal. Try the bleach solution thru the overflow holes. If you have city sewer, no worry about overdoing it on the bleach. With septic, be a little cautious, but 1/4 cup of liquid chlorine bleach with some water is not going to hurt the septic system bacteria.
 

LLigetfa

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Bleach alone is likely to be a short term fix. You really need to scrub the pipes with a brush. Not many folks fill their sink up to the overflow.
 

Paul Blakely

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After 4 to 5 years trouble-free, we're now frequently smelling sewer gas from the bathroom vanity sink. The only thing I can think of is that the p-trap must be siphoning out. Is it because the 13" length from the bottom of the sink to the bottom of the p-trap is too long?

It's been 6 years since this remodel, but I'm pretty sure the dwv vent pipe on the other side of the wall properly goes down to the main drain and also to the upstairs bath and out the roof.

Would an AAV help? It looks like there would barely be enough room to install one between the trap and the wall.
Well lads, thanks for the advice to take it apart and clean the trap! I was astounded by how gross it was. I'm sure that fixed the problem - and it was something I hadn't even considered. I LOVE THIS FORUM!!!!
 
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