I have just got done reading this thread, great answers by everyone.

I too have just recently developed an odor under my kitchen sink.

Just a week ago I replaced the kitchen sink and faucets. Not long after I replaced everything I started smelling an odor that I think is sewer gas. You can't smell it from the on top in the sink drains (double sink, disposer on left), but it hits you under the sink. I have my traps in both sinks, dishwasher drains to the disposer. I checked for leaks, and there is nothing.

My PVC pipe drains through the back of the cabinet.

Even though I didn't really disturb the main pipe when I changed everything out, I'm thinking that the vent pipe beyond the cabinet could have somehow been loosened, or maybe the drain pipe on the elbow maybe was loosened... just on the top.

My question is what does the vent pipe look like? I'm assuming it's just a PVC pipe coming out of the top of the drain pipe.

I haven't opened up the back of the cabinet yet, but I'm figuring it's my next move.

Any comments, let me know.

I too live in a new home (we renovated it completely) and there is a weird musty smell that I cannot identify coming from the sink area. I can smell it under the sink and near the light switches mostly. It is our bar sink though and is only used about twice a year so I can't imagine there would be a leak anywhere? There is no warping under the cabinet where the sink is. Please help!

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Originally Posted by hackshawash

I too live in a new home (we renovated it completely) and there is a weird musty smell that I cannot identify coming from the sink area. I can smell it under the sink and near the light switches mostly. It is our bar sink though and is only used about twice a year so I can't imagine there would be a leak anywhere? There is no warping under the cabinet where the sink is. Please help!

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Bar sink has a P-trap. Trap has standing water in it to prevent sewer gas from entering living areas. That water will dry out and your sink drain will automatically become sewer vent. Solution: run water in the sink at least 1 x a week to keep P-traps wet.

Also, each drain should have vent. Vent should either terminate above the roof or close to the P-trap via AAV device. It may be that the plumber left vent pipe open inside the wall. I am assuming that based on your comment that you can smell sewer gas "...near the light switches...". Solution: cut open wall under the sink and inspect pipe going upward from San-T. See if you can determine whether this pipe continues upward in one piece or if it was left open. If you find out there is AAV device, you may replace it since it may be not working properly. I am enclosing sketch of typical drain/vent/p-trap detail to better illustrate the point...

Let us know what you have found out... Good Luck... Milo

Wow thanks for the quick response Milo! I can't wait until my husband gets home so we can look into it. One more thing, there is a large window right above the sink (it goes about a foot wider than each side of the sink) so could there still be a vent here? Maybe that is the problem. I took pictures of all the walls before they closed them up (although the insulation covers a lot of it). I attached the photo although you can't see much but maybe you might see something I don't in it! I labeled it for perspective!

http://i195.photobucket.com/albums/z.../Drainwall.jpg

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Originally Posted by Milo Dolezal

Bar sink has a P-trap. Trap has standing water in it to prevent sewer gas from entering living areas. That water will dry out and your sink drain will automatically become sewer vent. Solution: run water in the sink at least 1 x a week to keep P-traps wet.

Also, each drain should have vent. Vent should either terminate above the roof or close to the P-trap via AAV device. It may be that the plumber left vent pipe open inside the wall. I am assuming that based on your comment that you can smell sewer gas "...near the light switches...". Solution: cut open wall under the sink and inspect pipe going upward from San-T. See if you can determine whether this pipe continues upward in one piece or if it was left open. If you find out there is AAV device, you may replace it since it may be not working properly. I am enclosing sketch of typical drain/vent/p-trap detail to better illustrate the point.....

Let us know what you have found out....Good Luck....Milo

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Hackshawash: Yes, indeed, many times sink is centered on kitchen window. In this case we install so called "dirt arm". Basically, what it is an unvented horizontal drain pipe that connects to San T , located on side of the window and past by structural Trimmer and King Stud ( window framing ). Therefore it connects to Drain/Vent pipe. This horizontal pipe should not be longer than 5' for 2" pipe and 4' for 1 1/2" pipe with slope of 1/4" per foot. See the drawing to illustrate the point...

Thanks you for posting the photo. I cannot see whether it is installed correctly because there is insulation in walls. Peal it off off and see what's there... Maybe you could take another photo and post it for us to see. Thank you. Milo

That photo was from a year ago. There is drywall and cabinets in front of it now. Now I wish I'd taken photos before the insulation was in! One more question. Does the pipe going up to the vent have to be in line (i.e. directly on top of) with the pipe going to the sewer or can it be offset? Thanks for the help!

If it is not decaying food or a deceased animal that is causing the smell, it is most likely an odor from a mold problem that could be growing in the cabinetry wood or walls around the sink. This is often a problem where there is a pipe leak (whether large or insignificant) or simply where humidity is high. I would look closely to see if there is mold growth around that area. When you smell it, that means that is has reached the surface somewhere, dried up, and became airborne so that you breathe it in.

Well after 18 months,a plumber and replacing a garburator and all the pvc under the sink twice the smell under my sink is gone thanks to the persons that mentioned the black rubber connector from dishwasher tube.Must have been off gasing or something. Actually when I first moved in I thought it was the carpet underlay that was stinking up the house so I replaced all the old carpet and underlay. Same kind of smell. Thanks again folks!

Another possibility I have come across a few times is that threads have rotted out on galvanized pipe being used as the vent. You could drop some peppermint extract down the roof stack or do a smoke test to find out.


Sorry if I restated anything. I didn't realize there were seven pages of responses until just now

Time to put this six year old thread to rest guys. Tom

Well... hopefully Rusty (of the original post) has moved on since '04, but I'll add my findings in order to maybe helped the next person with a stink under their sink.

For me, it seems that problem stems from a small obscure leak from the [lifetime] faucet that we wetting the inside back panel of the sink base (cabinet). As is mentioned else in this thread, there ~should~ be a distinguishable difference between the smells of a dead critter, sewer gases, mold/mildew, and... wet luan/plywood or compressed wood. However, when you're having trouble identifying the source, you start to second guess your nose.

Having found the leak and the warped luan, I can 100% WITHOUT A DOUBT believe that I found my problem... unless it doesn't go away then I'll start to re-think the dead critter possibility.

Just wanted to say I had a strong musty smell coming from under my sink as well and I think I figured out the problem. I took apart the pipes from under the sink and found that a muddy substance was sitting on the trap ( I guess that is what it is) A while back I repotted a plant and I washed some potting soil down the drain and it turns out the soil stayed stuck in the trap. :( Lesson learned don't wash dirt or potting soil down the drains.

O.K. I also had this smell under kitchen sink. No leaks, removed a few dead rats from crawl space, used "drain care" through drains and dishwasher, used clorox, ran hose down vent pipe... the answer... that same smelly black hose that runs from the air gap to the disposal. Ours had a sag in it that may have allowed food to rot in there... funny, it didn't seem to smell that bad... maybe it gradually gives off the smell and when you open the cabinet, boom! Anyway, replacing this hose solved our problem (disposal was replaced too--it was really loud) but I think it was the hose.

Roshoi, roseande and jimheyek,
Same complaint different solutions.
We thank you for your input. '
Your solutions should help many people with the same problem.
Thanks again, Tom