Reach and wash system is the fastest and safest way of cleaning windows, using the purified water, which is filtered by either a two-stage or three-stage filtration process, involving a carbon filter, and two de-ionization filters, or a carbon filter, a reverse osmosis membrane filter, and a de-ionization resin filter. The filtered water should contain a TDS (total dissolved solids).Because there are no solids dissolved in the water, the windows dry clear without water spots.