I have 3 water drain valves on the large storage bay/drawer side, and I'm not sure what 2 of them are for. I do know the back one is for draining the fresh water tank. The other 2 may be for blowing out the lines for winterizing?? Any thoughts? Also, the fresh water tank drains very slowly. I was having problems filling the tank, so I checked the hose under the bed and found it bowed in the middle. I supported it all along the run and made sure it sloped to the tank, and that corrected that problem. I also found a kink in the overflow/vent tube just outside the water tank, and the tube was full of mold. I replaced this tube with a stronger tube and made sure it drained properly. I thought that might improve the drain flow, too, but it had no affect.