When I use the Lysol for the final cleaning I fill the tank 1/4 full with clean water and 1 complete botle of the red lysol liquid and a bag of ice cubes. After dumping this swirl I then flush the tank with clean fresh water and leave the valve open overnight to dry out. The next morning I close all water drains/valves. As proof of this procedure I recently had both dump valves replaced and the repair facility said not only was the tank empty but it had no smell and it was dry.