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!