The first layer of the replacement filter activated carbon and oxidation reduction alloy removes the chlorine taste you are accustom to with tap water. The ion exchanges stage removes virtually all dissolved solids that may be left over from public water systems or even leached into your water from piping such as aluminum, lead, zinc, nitrate and more. Three additional stages are included to remove other impurities and to ensure your water receives the appropriate amount of treatment time to deliver a "00" reading on your laboratory-grade total dissolved solids meter included.