The Whirlpool WHEERM is the UltraEase replacement membrane for the Whirlpool WHER25 Reverse Osmosis System. The Whirlpool WHEERM RO Membrane has been certified and tested against NSF/ANSI standard 58 for the reduction of total dissolved solids TDS and organic matter and has a rejection rate of 90-95%. The Whirlpool WHEERM Reverse Osmosis Membrane typically lasts a year depending on your water s pH level and hardness. The membrane should be replaced after a decrease in water pressure or quality.