I recently purchased a 2003 Forest River Sunseeker Class 'C'. There are two (2) fresh water hose inlets on the side of the coach. One is "City water", and the other is "Fresh water tank fill".. The fresh water tank is inside, under the bed, and ABOVE the level of the outside inlet. The tank is sealed, except for hose and breather tubes. How can I get sanitizer solution into the tank? Rinsing later will be no problem. Can't tell if there is a antifreeze bypass anywhere.