After we dump we put about 1/3 tank full of water and then we put 2 cups of Twenty Mule Team Borax laundry detergent and 2 cups of Pinesol in our black holding tank. Then as we drive to the next location the solution slushes around the tank and cleans the insides. When we store the coach we again put this same mixture in the tank. This has eliminated the odor for us.