REVERSE OSMOSIS STORAGE TANK - 2.2 GALLON (8.33 Litres) Specific steel tank designed to keep RO water after treated for reverse osmosis. This tank is of good quality metal NSF. It is possible to make a vertical installation or also to the horizontal. It is also possible to connect several tanks of the same type one after the other to increase the capacity of water supply. The inner membrane is made of butyl rubber, food standards, and is pre-swollen in the factory. The volume of the tank is 2.2 gallons is 8.33 litres, but the actual volume of pure water is between 4-5 litres.