25 year old house, Washroom waste pipe (copper) is first ,(or last) connection on the waste line before the exit main (cast) to my septic system outside. I can smell that sewage smell in the room, and in the washer tub. I just had the cesspool drained/cleaned/inspected/ in August. What does this mean? Can I add Ridex to the system? Does that help? I don't have that smell at any of the sinks, or in the basement.