After you finish your spraying duties, empty the tank and make sure you dispose of any leftover chemicals properly. Add a small quantity of dish soap to the tank, and add some warm water. Close the tank, but don't pressurize it. Swirl the water around and rinse before repeating. On the second cycle, pressurize the tank and release the water through the wand. After it's clean, rinse with fresh water and store it away.