Hello, I live where winters get very cold and when it is below 10° F and we make laundry and/or take showers, it smells really bad in the basement. The vent stack is not frozen (I insulated it outside and in the attic) and I don’t have an empty drain or p-trap anywhere in the basement. It never happens in warmer temperatures. I have a septic tank system and never had any problems. Any ideas why this happens? I know I should be having a smoke test done, but I don’t understand why it only happens in cold weather if the stack is not frozen… Thanks.
We do not work often with septic tanks where we are located, but a smoke test would be our first recommendation. My team of plumbers also feels that it is odd that the smell only occurs in cold weather. Please update us when you do figure out what is causing the issue. Best of luck!