Hydro Logic 22045 Evolution RO1000 RO Membrane Element The evolution reverse osmosis membrane element 22045 is the replacement ro membrane for the tank less hydro logic ro system Membrane 22045 has a packaged shelf life. It is best to order when you're ready to install them The evolutionro1000 system requires two of these membranes to operate should be replaced every 6 months to 2 years