The Assault 3 stage cart is configured for optimum pure water cleaning, providing up to three floors of cleaning power under regular tap pressure with no pump required. Water enters the purifier through the carbon filter, which removes the chlorine and other chemicals. It flows through the reverse osmosis (RO) membrane which removes approximately 85% of the total dissolved solids (TDS). From there it enters the deionization (DI) filter which polishes the water and brings the TDS level down to or close to 0. This process provides 100% spot free water for cleaning and rinsing. It eliminates spots from occurring on the glass. In addition, it provides purified water for a much longer time than regular DI filters, before filters are required to be changed. Note – It does remove pre existing water stains. If this issue is prevalent a chemical clean is required.