check for something coming back up the pipe into the sump pit and dying. in the
spring, little peeper frogs would crawl 50 feet from the back yard thru the
discharge hose into our sumps and sing all night. Something bigger like a mouse
or rat could get in, get stuck, and die.
We also thought we had a sewer gas leak in the basement that turned out to be
some shrink-wrapped hamburger that was accidentally left out for over a week,
hidden under an empty cardboard box while we were busy re-arranging foods in
the downstairs fridge.