Reverse osmosis (RO) is a filtration method that removes many types of largemolecules and ions from solutions by applying pressure to the solution onone side of a selective membrane forcing only the small water moleculesthrough the membrane becoming purified or permeate water.Membrane surface is always kept clean and unplugged by ‘Cross Flow’operation that happens inside membrane element. By means of ‘Cross Flow’,while some liquids (element water) pass through membrane, some liquid(intensive water) move parallel to membrane surface, so protect othersto stick to membrane. This process enables much more qualified watercompared with other filtration systems.