Sewer gas around sewer clean out plug
With this being my second post in plumbing in two days, you can guess what is my weakness!
I've posted before about sewer gas coming in around the main clean out plug in our basement. I had that fixed when a plumber was here for another project back in September. The problems came back in early December and the smell is driving me nuts again. We've had delivery people come in and think we have a natural gas issue in the house.
I am not sure what exactly is the problem (PLEASE Help!), but to temporarily solve the issue, I put a plastic bag over the drain line cleanout plug and used duct tape to seal it as air tight as I could. Within a short period of time the bag inflated under the tape. I can push on it and air hisses out around the tape, and then the bag reinflated.
1. Why would there be positive pressure in the sewer line heading out through the basement floor vs the unfinished basement?
2. I believe when the plumber was here he used plumbers putty to try to seal the cleanout cover. It worked for a while and then got worse again. How can I seal this in a more reliable manner?
3. Does this pressure gradient indicate that there is some other problem going on in my sewer system?
ANY advice would be greatly appreciated!!!