Permeate Pump : ERP 500 for Reverse Osmosis Water FIlter Systems | Reduce RO Waste Water Powered only by the hydraulic energy of brine water usually lost to the drain (i.e. no electricity required). The ERP 500 is a much quieter alternative to the ERP 1000. The water TDS is also a lot lower. The pump forces product water into the storage tank, reducing membrane back pressure and maximizing available feed pressure Permeate Pumps can bring storage tanks up to line pressure and then shut the system down when these tanks reach capacity, eliminating the need for a hydraulic shut-off valve. Other benefits include higher delivery pressures, faster R.O. water production, superior water quality, and extended filter/membrane life.