We have a basement laundry (washer and utility sink) with a sump pump in the ground. Water from the washer and sink are connected to the sump pump. The drain is above ground until and then dives into the sump pump. A vertical pipe extends from the pump, then turns horizontal then goes out to the sewer. There is no pea trap between the pump and the sewer. And no pea trap between the washer and the pump. When the tank fills the pump turns on and a big gush of water goes up the vertical pipe and drains out the basement wall like a normal sump pump. Whenever we run the laundry, the entire basement smells like sewage. We have lived in the house for two years and have always had the problem. Any ideas on what could be causing the smell an how to fix it?

Is there a check valve on the discharge line?

there should not be a p-trap on the outlet side of the trap. there should be a check valve there.

I just looked. There is a check valve on the horizontal part of the discharge line.

next question is.. is the check valve working? or.. after the pump shuts off do you get a bunch of water draining back into the tank?
assuming that the check valve is working then you are not getting sewer smell back from the discharge pipe.
all that leaves is the accumulation of gunk etc inside the tank smells and is coming back thru the untrapped sink drain.

Washing machines that discharge to sump pumps always put out a horrendous smell at the sump. When making service calls to a house with the set up that you have, I can usually smell that distinct odor as soon as I step into the house. It's not a septic tank odor but just as foul (rancid).

We get some water draining into the tank. there is about a 1-foot of water in the bottom of the tank. I just looked and the water is super gross with about an inch of sludge on the bottom. It smelled when I opened the sump, but room doesn't smell when the washer isn't running.

if the tank lid can be sealed and vented to the outside, that will take care of the smell when the washer is discharging.

Good idea. I think we will clean it out and then vent it.



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