We recently purchased a 2008 Sundance 2900 MK 5th wheel and the dealer filled the water tank so we could check out the trailer. However, when we went camping our first trip and tried to fill the water tank, it would only take 1/3 of a tank. The fill tube would fill up completely to the top with water and splash out. We could hear water dribbling to the tank below. We discovered that by disconnecting the tank vent hose and blowing into it, we were able to then fill it full. It appeared that something may have been dislodged from that vent tube. But now we are concerned that if there is an object in the tank, it could block the vent tube, the drain tube, or the tube leading to the pump. Has anyone else had problems?