Water goes through a reverse osmosis membrane very slowly and people don't have the patience to wait a long time to get a cup of water. For this reason the residential RO units need a water storage tank to store the purified water. The RO tanks can delivery stable and constant water flow when the faucet is opened. The concern that pollutants might come from air or animals with the use an opened tank favors the use of a closed expansion tank.
Lead leaching to drinking water the cause of health risks, brass and copper are banned for use in purified/drinking water. All TANK PRO expansion tanks use stainless steel connections to avoid the lead leaching concerns.
To avoid bad odors from diaphragm, all of our diaphragms are post-cured before assembly, to eliminate the possibility of odors from the tank.
Our tanks are NSF approved under standard 58, and CE approved under the PED (pressure equipment directive), because of these approvals our tanks carry the appropriate markings and can be used everywhere in the world.