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Sewer Smell from Below Kitchen Sink When Showreing

16 years ago

Hi, newbie here! I'm a total amateur when it comes to plumbing, so I thought somebody here could help me out. When we use the upstairs shower, a horrible sewer smell comes out from under the kitchen sink. The shower is located in the room directly over the kitchen. Nothing out of the ordinary as far as the shower is concerned. We do have a problem where some of the traps throughout the house dry up and we have to run some water in them. It's a pretty big house and some of the sink don't get used for weeks, so I'm not too worried about that. You can see a couple pics from the link.

As you can see, there are holes cut out in the back of the sink for the pipes. I thought the smell may be coming in from the hole from another part of the house, but I sealed the holes with plastic , took a shower, and the smell was just as bad.

More info: There is a dishwasher and a disposal installed. Both of these are brand new, so I think I can rule them out. The smell does NOT come up from the kitchen sink drain. Not sure if you can tell or not, but the water drains through the floor and not through the back. So I'm hoping that I've narrowed it down to that piece on the left (2nd pic) that is capped off. I'm not sure what the function of that is. It has a NOVAVENT cap on it. Is it possible that the leak is in this piece. Does the NOVAVENT cap let air in. Could it possibly be letting air out?

Also, I found some vents terminated in the attic. Not sure where the main vent out is.

Anybody have any more suggestions?

Here is a link that might be useful: Pics of Sink

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Comments (2)

geniere
16 years ago
I am not a plumber, but I think I know what is happening.

The "cap" is a vent to prevent a vacuum forming in the sink drain. It is spring-loaded and, without water flowing in the drain, does not allow air into the drain nor allow foul gasses out.

My guess is the short horizontal run of pipe from the "T" to the vent is clogged. When the shower is running, the drain water forms a vacuum in the waste drain system. This vacuum pulls water out of the sink trap allowing the foul gasses to escape through the trap and sink drain. An unclogged vent would have opened and "killed" the vacuum.

I believe your sink drain is improperly plumbed as far as venting. I suspect you have the infamous "S" trap rather than the desirable "P" trap and also have a problem with the bath drain venting
matthew2
16 years ago
from what i know of venting systems it appears that the "pop" type vent you have is installed to low. i believe they are recommended to be at least 6" above the dirty arm,
that's the pipe going to the trap.
your pics show it being on the same plain or below. find out the make and check with them for proper insall.
i am a plumber in az. and have been in the trade 20+
best of luck
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Did anyone inspect the vent pipes to make sure they were installed correctly? Try also posting this on the Plumbing forum. I found this on another web discussion site: "It may be that you have a leak in the sewer stack, and that the expansion with the hot weather is whats causing it. Cold weather contracts various things and may seal it up again. I too am the type that I can smell things in parts per billion (reason why a lot of times, the Superintendent would ask me how the plant was doing, because I was the first to be able to detect things at the Waste Water Plant). Another possibility is that something is in your attic and its coming down through cracks in the ceiling or through the walls, in your bathroom, (dead squirrels or some critter). Now, make sure, to check your TRAPS in the shower or bath. its possible, that you have a plugged up soil stack, (though the plumber should have found this, if he checked the roof), and that when the temperature gets warm, or something happens outside, it sucks down the water from the traps in your bathrooms, (like when you use your sink in the kitchen and it creates a vacuum and draws down the water from the traps if the pipes aren't big enough...)"
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