My sump pump pit emitted a foul smell each time the washer or water softener discharged larger amounts of water in it. My first wild guess was probably some organic deposits on the bottom of it that needed to be cleaned. Quick background history, I bought the house a year ago, spent half of that time remodeling it as it was in a sorry state. Prior to that the house was owned for almost 10 years by one of the worst DIYers who also was a heavy drinker. Everything done to this house in the past was messed up beyond any comprehension. So I wasn't surprised that the sump pump pit was left unmaintained.

On the cleaning day I pumped as much water out of it as I could and proceeded to remove the remaining water with a small bucket. That's when I ran into several "surprises":

The pit before pulling the pump out:


Getting stuff out: copper 3/4" pipe, 10lbs weight plate, random pieces of metal, glass, small stones, electrical wire strippers (not shown):


Large random piece of concrete:


In total 3 paving bricks, pulled another one later on:


Sump pump in a sorry state:


Overall, the pit deepened quite a lot after removing all the sediment. In total, I pulled out about 1.5 bucket of foul smelling greyish slime. The smell stopped, water in the pit is clear now. Overall, I'm glad I finally got around to clean it up especially since it's Winter and the heating furnace sits right next to the pit.

 

Your washer dumps into the sump pump? Where does the sump pump drain?

 

Sump pump drains into the main sewer pipe.

Edit:

This sump pump discharges to the main sewer. It collects water from the utility sink, A/C, and water softener. This is I assume the original sump pump pit that was put in place when the house was built.

There's a second sump pump pit that collects water from under the house and that one discharges through an underground pipe to a rain water sewer out in the street. That one, my guess is, was added sometimes in 90's when the previous owners installed the drainage system.

 

Technically that is not a sump pump system. It's a sewage ejection pit and as such is usually a sealed top system with a vent pipe.

A sump pump system is used for water under the slab and rainwater removal. The pit is usually shallow and not vented. It pumps the water outside but never to the septic/sewer system.

 

@PJmax

Thank you for the clarification. You basically described the setup I have in place.

The sewage ejection pit has a vent pipe but it wasn't sealed (working on it now).

The sump pump collects water from under the house, it isn't vented, and it's pumping out to the sewer.

Now this brings me to a question of argon gas. The area where I live is, according to government statistics, is higher than average in argon gas ground emission.

Should I vent the sump pump to the outside just like the sewage ejection pump is?

 

You mean..... it's not pumping to the sewer. (Maybe to the storm drain in the street)

I don't how effective venting the sump pit would be.

 

The sewage ejection pit needs venting because it is supposed to be sealed so as to not let vapors and odors into the basement.

The sump pit should not emit odors (provided you don't pour washing machine suds or water softener brine let alone sewage into it) and does not need to be sealed. Then it does not need a vent pipe. (For argon/radon mitigation it may be necessary to seal and vent a sump pump pit)