The Solution valve is where fluid leaves the Clean water tank and enters the Scooba. The first picture is is of a good tank. Notice the rubber gasket and the gray cap at the bottom of the valve. A filter screen is also visible.

The second photo is a wrecked tank. Parts can be seen in the tank. A sharp rattle like screws hitting plastic will be noticeable if the tank is shook. There will always be a dull thunking rattle.

The third photo is the port on the Scooba. If the tank comes down on this port just off center, the valve can be pushed into the tank, and the tank becomes useless. Always make sure the tank is seated squarely in the tank receiver when closing the tank onto the Scooba.