How Does the R.O. System Work? Reverse Osmosis (R.O) in one of the most convenient and economical methods of reducing unwanted contaminants in your drinking water. Reverse Osmosis is the process by which water molecules are forced, by household pressure, through a semi-permeable membrane. Most of the impurities and other contaminants are rinsed to the drain while the refined water is routed to a special holding tank. Our systems direct the flow of water through each filtration step without the need for tubes or fittings. This design also contains major component parts like the water saving automatic shut-off, drain control and safety check valve, making it easy to maintain and service. Another innovation is the membrane seal. This feature makes membrane replacement a snap without the need for tools. The Lancaster Reverse Osmosis system is designed for the use with water that is reasonably free of contaminants that can clog or damage filters of the R.O. system. Contact your local Lancaster Water Treatment dealer for a water test to determine the best R.O. system for your home as well other appropriate water treatment needs.