septic smell

About 3 days ago, I began smelling an intermittent septic-like smell coming from the pictured wall. General layout info: We live in a one story ranch with a partial finished basement. The furnace/main mechanical room is near but not directly below this bathroom. The "smelly" side of the wall is...

We purchased a 35 YO house a year and a half ago. About 6-8 months ago there started to be a really bad septic odor that seemed to be coming from the upstairs guest bath. We have a septic system that was inspected thoroughly by a consultant when the house was purchased and tank was emptied at...