Calcite is a naturally occurring calcium carbonate media. Calcite neutralizes low acidic pH conditions and re-mineralizes reverse osmosis water. These cartridges will make water less aggressive and many prefer the pleasant taste added to drinking water. The media is dissolved during filtration, thus the cartridge should be replaced prior to complete depletion. As the Calcite's calcium carbonate neutralizes the water, it will increase hardness and a softener may become necessary after the neutralizing filter.