My basement is open to the rest of the house so any smell makes it's way upstairs. It's a 3 bedroom + one bed downstairs and has had 4-5 people living in it. I don't know what size the septic tank is but I just found a chart that for the largest size tank, it is due to be cleaned out. We've been here about 6 yrs. + 1 month. (New house.) For the past week the whole house smells like sewage. I can't figure out where exactly it's coming from. We have 2 sump pumps but the washer is upstairs so they don't run. We covered the 'vent' holes with plastic cups to keep the ping pong balls out of them. I couple months ago we had a problem of urine smell and I discovered my young teen was being too lazy to come upstairs to use the restroom and was using a cup and pouring it into the sump pump hole. Never again! I poured about a half gal. of vinegar and let it set for about an hour and ran a hose to it and ran both pumps a few times. With a window open, the air got better. This smell is definitely different however when I lifted the cups, I can still smell some urine odor. (So I ran the pumps again.) (I didn't put the vinegar that time, though.) Is it possible that this is caused because I need to get the septic tank cleaned out? The drains smell fine. And the water goes down the drains fine. Can it come through the walls? Help.

We covered the 'vent' holes with plastic cups to keep the ping pong balls out of them. You're going to hafta explain that one, Your vent pips exit the roof. What are you doing with ping-pong balls up on your roof? Do you have a floor drain in the basement?

I discovered my young teen was being too lazy to come upstairs to use the restroom and was using a cup and pouring it into the sump pump hole
Have you considered that your lazy offspring might be craping down there and hiding it?
The solution would be to paper train and housebreak your son. Good luck with that! Tom