My house is on a well. I have a brand new sump pump. I am on public sewer for my town I do not have septic tank. I know it has no bearing on the sump pump. I have an ejector pump that is hooked up to our laundy tub. Is like a closed container with a pump in it and the water is pushed up pvc piper that go up .when the washer drains into the laundy tub the ejector pump goes on and pumps it somewhere, t What is the purpose of this pump. I have noticed sometime it get a bad smell int the conatiner. But when I run the laundy tub it goes away. What is causing this and how can I stop this smell it is like bad old stilling water.Is there a way to put something in this like a septic tank cleaner? It happens every once in a while. Someone told me it like a mini sump pump and I should replace the charcol that lines the bottom. Why kind of charcol do you buy for this?

Do not add anything to the sump pump. Do not put charcoal in there. Try to caulk the seals of the sump basin [container].

Doug is 100% correct, seal the container. Does this pit have a vent? It should. You have a pump because it appears your washer drains at a level lower than your exiting sewer line or it is nowhere near a sewer drain and needs to be moved a long distance to reach a sewer line. I'd have to see it to tell you for sure.