Thanks. The tank is a glass 4'x18"x24"h and is drilled on the bottom in each back corner and then connected with bulkheads, 1 for water in and 1 for water out. The one on the right has a 1" pvc pipe that comes straight up and is about an 1" or so below the very top of the tank so water siphons off the top of the tank to the sump. Not too often, but once is enough, a snail or something goes down and gets stuck so the water gets pumped down in the sump since it isn't returning. The sump is in the basement along with the pump and when this happens the top off water float senses the low water in the sump and makes the water rise in the sump to where it should be. As you can see the pump keeps on sending water up to the tank and then comes a waterfall. Not good this morning. Luckily I was home. I'm planning on taking some pics but haven't gotten to it yet. I definitely have to make this fool proof. Thanks for any help.