I getting a 800 gallon DairyKool Thank that has a spray head inside the tank. I was told it is a self cleaner. Now I believe what they mean is it has a unit that runs the pump that sprays a cleaner in the tank with a rinse cycle. Now what is confusing me is the electric pump that is mounted on the lower left bottom on the outside of the tank that has hoses that run into ports on the side of the tank. They must have plumbing on it inside of the skin of the tank. They are controlled by a box on the wall.