We usually throw a pod of laundry detergent down the toilet when we set out on a trip, add a little water and let it do its thing while we drive. Detergents are polar and will work to dislodge anything built up on the walls of the tank, and will work to break up any solids in the water. I hear the full timers using jus water, that's fine. But laundry detergent is cheap, and putting 1 or 2 pods down the toilet is easy. For those of us who's RV's get less constant usage it's probably not a bad idea to use it. It certainly wont hurt anything.