It empties perfectly fine. I have a 2009 Moomba XLV. The Ballast system says Gravity on it (I assume that's the Manufacturer). The pump turns on and acts like its filling for about 5 seconds then shuts off.
My assumption is that if there was a clog somewhere it wouldn't empty. I was hoping to WakeSurf on Fathers Day yesterday when my Ballast wouldn't fill. The hose coming out of the pump takes a quick right turn ( its kind of Crimped) to get to the Bag Compartment...A questionable design flaw...Any Thoughts out there of what this could be. Thanks..