
Water goes through a reverse osmosis membrane very slowly about Maximum 0.13 Litter per minute with membrane 50 GPD) and because people don't have the patience to wait a long time to get a cup of water. For this reason the home / residential Reverse Osmosis Systems need a water storage tank to store the purified RO water. The reverse osmosis 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.