We are going to be away from our 5th wheel for about 3 weeks. It is in an RV park. Here is what we plan to do: Turn off water to the trailer. Try to have an "as full as possible" black water tank, but empty the galley and bath holding tanks...leaving enough to flush the drain hose after emptying the black water tank when we return. Otherwise, leave it hooked up to power (has a surge protector). The reason for leaving the black water as full as possible, is to let it act as a septic tank does...i.e., give the bacteria a chance to work on the solids so that we turn as much to sludge, as possible. I never feel like we vacate all of the paper when we dump, so this way we are giving the bacteria a chance to work their magic. I assume the tank if vented, so there should not be any build up of pressure. Anyway, can anyone find any fault with this plan? If there is a better approach, please post...I want to do the right thing.