RO Membranes recommends changes membranes in your RO system every three years depending on your water quality and system set up. We carry the popular 75 GPD RO membrane from Dow Filmtec as well as a100 GPD and 150 GPD RO membrane. If you do plan to change the membrane on your reverse osmosis/deionization system be sure to also change the flow restrictor to correspond with the membrane flow.