When dry camping I fill the fresh water tank when arriving at our non serviced provincial parks. On a normal stay we might only use about half of the water in the tank. When leaving , I open the drain hoping to have it emptied by the time I get home. After a forty five minute trip, it is still running out. I can park it ( seems empty) and if I were to move it the next day there would be more draining ( guage shows empty) Any suggestions?