In order to reverse the natural tendencies of water and salt movement, and force clean water to flow from salty water, the osmonic pressure must be overcome, i. e.  osmosis must be reversed. In order to reverse this flow of water, membrane systems, and Reverse Osmosis systems in particular, utilize a special constructed semi-permeable membrane element enclosed inside a pressure vessel. The diameter of the pores or apertures of the high technology R.O. membrane is 0.0001 micron. Pressure is applied to reverse the flow of water, the source of which is usually and existing, pressure is applied to the feed stream, water molecules are passed through the membrane, while salts are retained in the feed. Thus, utilizing the principles of water and salts movements, and combining them with pressure and membrane technology, the natural osmonic flow of solution is reversed.