Sewer smell in bathroom sink

[hdtvluvr]

I have been having this issue off and on since we bought this house 3 years ago. This bathroom has 2 sinks with each on a different wall. The problem sink has the air vent under it in the cabinet because for some reason they couldn't tie it to the vent stack. The other sink is tied to the vent stack. I've had a plumber out here twice and they would come when there wasn't a smell - just like taking a your car to a mechanic. House has 3 bathrooms and the other 2 have the sinks tied to a vent stack. Each time the plumbers came, they replaced the air vent even though they said it appeared they were operating fine.

How can I resolve this issue? Should the air vent be higher? Is there something different that can be done?

 

[Reach4]

Do you use that sink at least once per week? If not, the trap could be drying out.

AAV may be defective. There are troubleshooting techiques. One would be to put a plastic bag over the AAV, and secure the bag opening against the pipe. That will stop smells. If the smell returns, it is from something else.

Or you could just replace the AAV.

AAV should pass air if you suck on it but not if you try to blow through it.

There could be a dead animal in the wall or under the cabinet. The bleach thing is easy, so try the easy thing first.

 

[Sponsor]

 

[hdtvluvr]

Sink is used multiple times a day.

If I replace the AAV, the new one would be the 4th. Original one and plumbers replaced twice already.

Smell comes out of the overflow hole of the sink.

 

[Reach4]

I suggest cleaning the passages in the sink. I envision removing the trap. Block the bottom of the chrome tailpiece with plastic sheet and a big rubber band.

Then use chlorine bleach with water, and fill the sink to over the top of the overflow hole(s). Maybe open the stopper, and use a plunger to force water to circulate out of the hole(s). The amount of chlorine bleach is not critical. I would go for about a cup, which should be overkill. I like overkill for this. Let it soak.

You could even consider a special brush, such as a test tube brush, that will fit thru the hole(s). Example https://www.ebay.com/itm/175493043568

Have a tub to collect the water below the tailpiece before removing the rubber band.

If the problem is a dead animal, consider isolating the lower portion of the cabinet with a plastic sheet. Sniff under and above the sheet to see which side of the sheet the smell is stronger.

 

[hdtvluvr]

I'll give the bleach cleaning a try but it will be a couple days before I can do it.

I was thinking that somehow the p trap was being sucked dry or at least enough to allow sewer gases to get by. The smell rises when the water is running when it happens and thus the p trap would be filling/full because of the running water. That's why I was wondering about the AAV.

 

[GReynolds929]

If the smell is coming from the sink overflow it's not the AAV, any decent plumber would figure that out quickly. The overflow has gunk and bacteria built up creating smells. Do what @Reach4 suggests and you should be good for a while.