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 NSFANSI standard 58 for the reduction of total dissolved solids and organic matter and has a rejection rate of 90-95. The 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 or when TDS reductions drops below 75.