Same here. Somebody told me it was a heater for water. I Can't remember.
I also have a pit built in the floor, in the basement. It too has some water in it. There's this thing in the pit, I think it's called a pump or something like that. So when there's so much water in the pit, this pump thingy moves the water to another place. I don't know where the place is, I just know that the water goes from the pit to another place.