Reverse Osmosis Reservoir Tank

http://www.waterfilters.net/Reverse-Osmosis-System-Bladder-Tank.html
The 3.2 Gallon Reverse Osmosis System Tank is the standard sized tank for most RO systems. It features a 1/4" NPT stainless steel connector at the top of the tank. There is a 1/4" end that connects to the top of the RO tank and there is a side mounted air valve for re-pressurizing the tank when needed or for measuring pressure. This tank is the same as the American Plumber 144165 and the Pentek 144165 RO tank. It is also known as the RO-132 tank. It has been tested and certified by NSF International under NSF/ANSI Standard 58 for material and structural integrity. A black RO tank stand is included with the RO tank. The actual water storage capacity of RO tanks is not the stated size (in this case 4.5 Gallons). Reverse Osmosis water storage tanks have an internal bladder and an air pocket. The actual water storage capacity will depend on the air pressure inside the tank, the water pressure and the shut off pressure. The storage capacity of this RO tank is closer to 3.2 Gallons.