Clean Tank with the Cap for the BISSELL CrossWave Cordless Max Multi-Surface Wet/Dry Vac. To Fill the Clean Water Tank, follow these instructions: The Clean Water Tank is located on the back of the machine. To remove, use the finger groove above at the top of the tank to grab and pivot the tank backwards Unscrew the cap from the bottom of the Clean Water Tank Choose the right BISSELL formula The Clean Water tank has a Large Area volume and a Small Area volume. Pick one of the measuring volumes that best suits the space that you would like to clean. The Large Area fill lines are for areas up to 700 sq ft. The Small Area fill lines are for areas under 350 sq. ft Use warm (140F/60C max) tap water and add the appropriate BISSELL formula. Tap water with hardness greater than 35 ppm is recommended for use in machine to ensure the Dirty Water Tank full detection sensor works properly Screw the cap back on the Clean Water tank. On the back of the machine, align the bottom of the Clean Water Tank with the grooves and pivot the tank until it "clicks" into place Clean Tank w/ Cap CrossWave Cordless Max 1620629