I have been in a house almost a year and have been battling a sewage odor that seems to be coming from my sewage ejector pump in the basement. The initial problem was very strong odor. I was amazed that this pit could put off that much odor given that we almost never use the toilet down there (maybe pee in it twice a month) and 99% of what goes through the pit is just soapy water from the shower. I then had a plumber re-seal the top of the system. Then had him do a smoke test and the lid and the pipes leading in and out were all smoke free. The smell problem dramatically improved. But I am left with about 5% of the same smell problem and it is still enough to bother me. It is coming from the corner where the ejector pit is. Not so much a sewer smell, but a swampy musty smell. After we got the lid fixed I was somewhat convnced that the odor must be some funky mold problem behind the walls. I even did cut into some drywall in various areas and it is bone dry beind these walls. Since then, on three occasions we have gone out of town for two weeks or more and the smell is 100% completely gone when we get back. It comes back over the first few days back and is pretty much constant after that. That is what convinces me we are dealing with a sewer gas problem and not some funky mold problem. If it were mold it wouldn't go away like that. Definitely associated with living in and using the house. Those two week periods have been in the summer, fall and winter. So it doesn't seem to be associated with the gas boiler (which we also had checked for leaks and we are OK there). Only thing left in my mind is a sewer gas issue. Plus it smells to me just like the smell we had when the lid was leaking, only much less now.

The interesting thing is that when we did the smoke test we did it by pumping smoke into the vent that comes out of the ejector pit and that goes straight up above the roof line. When we did that we noticed that smoke was pouring out of the main stack vent over on the other side of the roof. What follows is what I think the setup is behind my finished basement walls (I have checked what follows with the previous owner and he believes it is correct). In my basement against one wall going from left to right are six plumbing related fixtures. On the far left is a utility room with washing machine and utility sink, to the right of that is a bathroom with a toilet, sink, then shower, and then to the right of that is the sewage ejector pit in the right hand side corner. The main stack of the house runs down the same wall between the utility room and the bathroom. The utility room drains to the main stack. The bathroom drains to the pit. The pit pumps up and over to the main stack (this line has a check valve on it. The pit also has a vent that runs virtually straight up and above the roof line. The part that surprised me is that all of the fixtures (including the utility room fixtures) vent to a single pipe that runs all the way from the washing machine on the left all the way to the right hand corner to join up with the ejector pit vent. Is this proper? I thought ejector pits were supposed to be vented on a dedicated line. So when we pumped smoke into the pit vent on the roof I think the smoke goes down the pit vent, some smoke mat enter the pit but most of it goes across this long vent pipe to the utility room down to the utility room wet drain line which connects to the main stack -- smoke then goes up the main stack and out the main stack vent out the roof. This explains why I was amazed at the amount of odor the pit could put off -- it has a circuitous but unblocked connection to the sewer system. Does this sound like a proper venting setup? So there is a way to go from pit to main stack that does not involve the check valve. This fact is my main concern. Sewer gas with constant access to my pit. If you add to this that any pit both expels air as it fills with liquid AND SUCKS IN AIR when the pit pump kicks on, means my pit is probably sucking at least some of it's air from the route I describe, the rest coming from what it can suck in from the part of the pit vent that goes up to the outside above the roof. If I were to do it I think I would have vented the utility room fixtures straight into the main stack (at a point higher than the fixtures). Then have all of the bathroom just vent to the pit vent line. Then the utility room would drain and vent to the main stack and the bathroom would drain to the pit and vent out the same dedicated line coming out of the pit. My current setup, in my opinion, puts a lot of unnecessary hope and expectations on the ejector pit and its venting (and on the traps and plumbing in the bathroom) that they will work perfectly and keep out gases from the main sewer line when I could just completely separate the bathroom and the pit from the main sewer system altogether.

All the vent lines discussed are 2.5 inch PVC.
Thoughts and help very much appreciated.

I'm not a plumber in any way, but do you have traps for all your sinks and your washer? If you don't have a trap that would allow the sewer gases to come up out of the pit.

Just a little story about where you think the smell maybe coming from. When I was a kid I slept in the basement and I thought something had died in a corner which was the opposite corner from where we found the rotting animal. Smells maybe transported by wind currents in the home away from where they occur to accumulate in a stale area.

Hope this helps.

Hi Soolyman

The sewage ejector should have its own DEDICATED VENT. That means that even the basement bathroom fixtures do NOT connect into the ejector pit vent... period!

The basement bathroom vents should combine into one 2" vent (2.5" O.D.) and the washing machine vent will connect into that and then the 2" vent goes up and connects into the plumbing vent system (stack) a minimum of 42" above the 1st floor.

Hope that answered your question... ;)

Mark

Thanks Massplumber.

2 clarifying questions.

When you say the bathroom fixtures and washing machine can vent to one 2.5 inch line and have that line connect to stack at 42 inches above first floor, does "first floor" mean the basement floor or the floor above the basement ?

Also instead of connecting to the stack can that line vent to a high capacity Studor (AAV) vent?

Thanks again.

First floor means the floor above the basement floor.

Studor vents aren't allowed in my state, but if they are allowed in your state then you should be able to use the high capacity studor vent AND keep it in the basement as long as you keep it accessible for future removal/change out.

Mark

You de man, Massplumber.

I'll find out about state/local code on the Studor vent. Thanks.