We have a new house. Moved in 6 months ago. One of the bathrooms smells like a sewer. It's horrible! Some days A LOT worse than others. We don't even use this bathroom much. We do have a new septic tank.

I would call the people who installed the septic. Maybe something didn't get installed right or something. Is this a newly constructed house? Let me guess, it smells worse when its warmer outside? I had a friend who had an animal climb into the plumbing of the new house they were building and it died in there! At least start with who put the septic in. they may have a simple answer.