Sewer Smell In Guest Bath

House was built in 03 , started noticing odor in 06 . Only get odor in winter when temps drop . Vent pipe goes up inside wall & exits above ridge line of house roof . What could cause this odor to show up in cold weather . Rest of house is fine . Everything drains fine . House has septic tank & system . Thanks

Traps dry out in unused bathrooms, particularly in heating season which will allow sewer smell into the building. Run water for a minute in your sink, shower, etc. each week to keep the traps full.

Not dry traps . We always run enough water to keep traps full .

Senior Plumber

Your sewer smell could be caused by a wax seal on the toilet,not completly making contact with the closet flange and the toilet china..