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Here I am again with the sewer gas dilemma.

Lots of you have read my previous posts over the last few years about the sewer gas smell we occasionally have in our home. Many have suggested things, we've tried those things, and many others, to figure out where it was coming from, to no avail.

We just started a total kitchen reno. Decided to do all new drywall while we were at it, so we took everything out today down to the studs. This is a tri level home. At one end of the kitchen, you can see the vent stack running up through the wall. It runs from the basement, up through the laundry room, up through the kitchen, up through the upstairs bath, through the attic and out.

When the house was built in 1980, one corner of the basement was stubbed in for a 3 piece bath, but the bath was not actually built until my husband bought the home in 1990. He had a crew come in and build the walls, set the fixtures, do all the required plumbing, etc. There's been an off and on sewer gas smell in this house since.

Today, once we got all the drywall off, we were able to look down into the wall on that end of the kitchen. I think we've found the source of the sewer gas. The toilet in the basement bath was tied in to the vent stack with what looks like an "s" trap (can't tell for sure from our view from above; it could be a "p")and on the opposite side from the stack, that "s" or "p" has a length of 2 inch pipe coming straight up off of it (can't see where it goes below) for what looks like about 12 inches and it is open. Where the end of this open pipe is, is exactly where we have been smelling the sewer gas.

Thoughts? If I were a betting woman, my money would be on this being the source. Question is, how the heck do we fix it??

Thanks so much for any input or help!

Re: Here I am again with the sewer gas dilemma.

From what you're saying, the plumber who did the basement toilet left a 2" line open inside the wall. If this pipe is useless, and it certainly looks like that from your description, then go ahead and cap it. There is a cap for every kind of pipe, so find the right one for you.

Re: Here I am again with the sewer gas dilemma.

Normally this is where I'd suggest testing with a lit match but we can skip that and follow DJ's advice and install a cap. A 2" pipe will be about 2 3/8" outside diameter. If in doubt, buy a few sizes as they are cheap. Use the proper PVC glue to secure it. If you want to keep access for snaking a clogged drain line, they do make adapters that have a screw in plate / cap. You can also use a drain plug in the proper size.

Re: Here I am again with the sewer gas dilemma.

Thanks guys!!

Re: Here I am again with the sewer gas dilemma.

Interesting to read. Last night as I walked downstairs to get a bottle for the little one, I smelled the sewer gas smell in our house that I cannot figure out. Hopefully I don't need to rip down drywall to figure out my problem.

I can imagine how relieving it must be to have that figured out!

Re: Here I am again with the sewer gas dilemma.

Well, it will be a relief IF it is actually the source. Having a plumber come take a look tomorrow just to be sure. I'm 98% sure, and the replies from the others make my 98% feel pretty much like 100%, but, bless their hearts, they're going from my descriptions only so I want someone to actually SEE it before I cap it off. If it IS the source, I will have to do a few back flips...in my mind...because I'm too old to do them otherwise!

I hope you're able to trace your problem. I'd start with making sure there are "p" traps on every drain, and that none of them have gone dry. If you have a basement with a floor drain, put some water down that once in a while, too. You can get up on your roof with the water hose and run water down the stack, making sure it comes all the way through.(take the cap off your clean out and have someone watch to make sure the water is going on out to the sewer) There is always the possibility that there is a crack, a hole (hanging a picture, etc) a separation in one of the stack joints, etc. Try to visually inspect all of the stack you can get to. Go to the basement if you have one, and on up into the attic space and take a look. Think about where the smell is strongest, and look into that. You can smoke test the lines, or have that done, to see if any of that smoke comes out anywhere in the house, and to also make sure it comes out your stack. If it comes out in the house anywhere, you've either got a drain with no "p" trap on it, or a dry trap. Another thing you can do is a peppermint test. It takes 2 to do it, but may be of help. Get some strong peppermint oil and mix 20-30 drops of it into a gallon of water. Do this outside. Have someone on the inside of the house to be your official "sniffer". Go up on the roof and pour that peppermint water down the stack (leave the clean out cap on) and then stay outside while your sniffer goes through the house carefully to see if he/she can smell the peppermint anywhere. If he/she can, then that is the area of your problem. This is the ONLY thing we didn't do simply because we had located the area we thought it was coming from just by how strong the smell was. We were looking at wrecking out the entire wall in the basement bath to see what was up. Re-doing the kitchen just may have saved an unnecessary remodel down there.

Good luck!!!

Re: Here I am again with the sewer gas dilemma.

I am confused here, the toilet should not have a P or S trap in it. It should be a 3 or 4" diameter pipe straight to the stack, maybe with a slight slope down toward the stack. The toilet has a built in trap, any additional trap would trap solids and eventually back up. If there is a vertical vent pipe in the horizontal pipe between the toilet and the stack, it should be capped off. It should not even be there.

Re: Here I am again with the sewer gas dilemma.

You're absolutely right, Keith! The toilet does have the correct and required pipe over to the stack, but someone also has what looks exactly like a laundry stand pipe running off of a p trap down there. Plumber has been here this morning to give me an estimate on relocating some plumbing so I had him take a look. He agrees with me that this is the source of the sewer gas and that it should be capped off. I'm on my way to the hardware store to get that cap! 22 year old problem solved and all it took was ripping out the entire kitchen to find it! LOL

Thanks again guys for all the years of listening to me whine about this, and all of the ideas for trying to find it. Just never occurred to any of us that there would be an uncapped line inside a wall. Probably because none of US would have done such a stupid thing!!

Hope you all have a most prosperous new year!!!

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