I recently talked to a couple of septic pumpers who are getting flooded with calls regarding a strong odor of sewer gas in customers homes.
We’ve been experiencing an extended period of severe cold weather and evidently the main plumbing stacks are freezing. Warm moist air within the stack starts to form ice around the inside of the pipe and eventually becomes completely blocked with ice. The solution is to get on the roof and either use a snake or warm water to clear the line, but if the cold weather hangs around it may reform again.
The problem for the septic companies is they don’t do that kind of repair and most plumbers are not interested either. I recommended they contact a home maintenance company or a roofer who also shovels snow from roofs as they are equipped to get on the roof and clear the stack.
Hope this helps anyone out there that may run into the same problem.