I had mine running on HOB mode in my sump. About 2 or 3 times, it pumped about 5 gal of water all over my floor. I still have no idea why. I am still using it, but I changed its location so its completely in the sump, so if it goes bananas again, the water just spills back over into the sump. I know there are a few others who have had this issue before, just can't remember their names offhand. I think I paid about 75 bucks for mine from Big Als, doing it again I would have spend more to get a better skimmer.