Sewage smell from shower drain, trap has water, vent was snaked and was clear
We purchased a condo (built in 2001) in 2010. Right after moving in, we noticed a sewage smell coming from our master bathroom shower drain (no tub). We cleaned the drain and pipe (as far down as a brush would allow) with vinegar, enzyme cleaner, etc., but the smell would return. However, if we ran the shower for a few minutes, the drain would stop smelling, but again, the smell would return by the next day. After multiple consultations with plumbers sent from our warranty company and our condo association maintenance crew, we still don't have an answer almost a year later. Through it all, we noted the following:
- The smell seems to begin (we *think*) after any of the 3 toilets are flushed. Not immediately afterward, but it seems to be associated with toilet flushing at some point in the day. We have 2 toilets upstairs (the problem shower is upstairs), and 1 toilet downstairs.
- When we left for a 2 week vacation, we ran the shower for a couple of minutes before we left and made sure not to flush any toilets. NO SMELL when we came back (!!!!). We should vacation more often.
- There is always visible water (in the trap I assume) when you shine a flashlight down the shower drain. The water does not move/bubble/gurgle after flushing toilets. The toilets do not bubble/gurgle when flushed.
- The roof vent was snaked, and they said there was nothing found to be blocking it.
- One day when the drain was smelling, I snaked a long piece of paper down the shower drain and got a 'sample' of the water. When I pulled the paper up, it was wet and looked clear, but did smell like sewage. Don't know if the water itself contained sewage, or if it was sewer gas that had 'clung' onto the wet paper towel.
- The previous owners did not mention any of this in their disclosures. We do know that the shower drain has been worked on twice in the past because the shower was backing up.
One plumber said he could go searching for a leak in a vent pipe, and 'turn our bathroom into swiss cheese'...no thanks. One said he wanted to do a smoke test, which another said would be useless. One said there might be incorrectly pitched pipes. But I get the sense that they have no idea what's going on. Any input would be GREATLY appreciated. This has driven us crazy.