Pressure Tank is complementary with Undersink RO Water Purifier. Our tanks are generally made of food-grade polyethylene and can be molded in almost any size and shape. The filtered water is stored passively in the tank and must be re-pressurized by an electric pump every time water is drawn from it. The reverse osmosis system is controlled by a float switch or float valve in the tank to shut off water supply. An atmospheric tank is open to the ambient conditions in the restaurant so it is necessary to have a sealed lid and a sub-micron air breather to prevent grease, mold, fungus, and yeast from entering the tank.