On my 2003 MB Sports 220V the ballast (hard tanks) on the port side fills up (automatically) without me turning on the pump. Also, it does not drain when I turn on the pump to empty it. I believe the pump is a Jabsco Junior Puppy (no check valves with this system), and yes I have switched the Impellars and this does not solve the problem. I plan on switching both pumps to the Jabsco Ballast Puppies, but before doing so, I want to make sure that the pump is the cause to my frustration. My questions, if the pump is bad can the impellar spin freely, allowing water to flow into the tank? Also, are there any other ways that the tank could be filling? Visually, I see no leaks and I can't imagine that water could be filling up through the stern where I can manually empty the tanks by removing a plug. Suggestions or answers would be greatly appreciated.