The Basics of Reverse Osmosis and Pressure Reverse osmosis works by forcing water through a semipermeable membrane, leaving contaminants behind and producing purified water. For this process to be effective, adequate pressure is necessary to push the water through the membrane and optimize filtration. The standard minimum pressure required is around 40-60 psi (pounds per square inch)... https://romegamart.com/product/domestic-spares/pumps/