Nano filtration, in concept and operation is much the same as Reverse Osmosis. The key difference is the degree of removal of Monovalent ions such as chlorides. Reverse Osmosis removes the Monovalent ions at 98-99 %. Nanofiltration membranes removal of Monovalent ions varies between 70 to 90 percent with a 70 to 75% water recovery rate*. So what does this mean, water is measured in a few different ways. For Reverse Osmosis and Nanofiltration we used total dissolved solids. (TDS or PPM) if your water has a TDS or PPM number of 300 reverse osmosis with a 98% reduction your brew water should be at 6 ppm. With a Nano filtration system that same water with a 300 PPM would be around 60 ppm.