I have a strange problem. I have a 2007 Holiday Rambler 38 PDQ. I recently went out for a week and encountered a problem where my fresh water tank somehow drained most of it's contents into the grey water tank. It is my understanding that the fresh water can only enter the grey water tank though a drain. There is no fresh water leaking anywhere and the water pump only does an occasional burp so as to maintain pressure. I drained the grey water tank and refilled the fresh water and it has now somehow transferred most of the fresh water again to the grey water tank. I have spoken to a couple of RV repair techs and the consensus is that this is not common or even possible . Has anyone encountered a similar situation?