The day after moving into our recently purchased house in Oregon, we started noticing sewage smells on the back deck that were periodically overwhelming. We later began smelling it on the opposite side of the house as well. A new septic tank was installed prior to our arrival and the independent inspector thought it was off gassing and felt it would go away in a month. It didn't. A crack was noted in the old concrete tank at inspection pumping. It was removed and replaced. I watered all the P traps with no luck. Occasionally, the smell springs up in the basement bathroom as well.
As this got worse, we began noticing a sink drain on the main floor was draining slow. I pulled the trap and gooseneck and found a nasty plug of goo. The smell emanating from it was a musty, dank smell but didn't smell so much like sewage like we had noticed outside. It was still pretty nasty though. Cleaned and sanitized the fittings and replaced. The smell persisted so I flushed the drain with baking soda, vinegar, and about 3 gallons of boiling hot water. The smell then became much more intense and overpowered the bathrooms immediately above and below this one. It finally decreased in intensity after a week but still persists in the main floor bathroom where the original clog was and periodically involves the bathrooms directly above and below the main offender.
I'm not sure if these 2 issues are related. All drains are now flowing fine so didn't think it was a clogged main. Considered a venting issue but again, the drainage seems to be fine and haven't noticed shaking water in toilets to suggest a vacuum. The house was built in 1947. I'm not seeing cast iron pipes, only PVC. There are no trees or significant bushes between house and tank. Of note, the 3 bathrooms affected by the smell are directly in a vertical line on 3 floors, the middle main one being the worst. Also, the vent in line with those 3 bathrooms seems to be where the outdoor smell is coming from. We have a 4th bathroom at 1 end of the house in an add on attached apartment that is completely unaffected. It shares the same septic tank as the main house.
The septic people say the tank, pump, and drain field are fine. Had a plumber out who thought everything looked good, though he didn't put a camera in anything. As luck would have it, that was one of the few days when we couldn't smell much ha! :)
I'm at a loss as to what is going on or even who to call. Starting to get a little dejected. I don't know if I'm going crazy but the smells seem to get worse on nice days and better on overcast, rainy days. We don't really change our water use habits on different weather days. The more intense smells typically occur with high water usage, such as dishwasher, clothes washer, and showers. Any suggestions? Thanks all!
