In stages 3 and 4,Water flows through a bed of media made of a special high-purity alloy blend of two dissimilar metals - copper and zinc (KDF-55D ®, and KDF-85D ®.) KDF is a major advancement in water treatment technology that works on the electro-chemical and spontaneous-oxidation-reduction (REDOX) principles. Chlorine is instantaneously and almost inexhaustibly oxidized.
Tests on KDF/GAC cartridge have shown 99+% chlorine removal past 20,000 gallons of water. In comparison, carbon cartridges of comparable volumes drop below 90% effectiveness after only 4,000 gallons.
Kinetic Degradation Fluxion (KDF) is a high-purity copper-zinc formulation that uses a basic process known as redox (oxidation/reduction) to remove chlorine, lead, mercury, iron, and hydrogen sulfide from water supplies. Iron and hydrogen sulfide are oxidized into insoluble matter and attach to the surface of the media. Heavy metals such as lead, mercury, copper, nickel, chromium, cadmium, aluminum, and other dissolved metals are removed from the water by the electrochemical process. They are attracted to the surface of the media, much like a magnet. The media inhibits bacterial growth throughout the entire unit. In fact, it has been shown to be reduced up to 90%, eliminating the need for silver, which is commonly used in carbon-only filters (silver is considered a pesticide by the EPA and, as such, must be registered with them).
Is copper or zinc added to the water in any significant amount? On 2.3 ppm chlorinated water, <0.05 mg/l copper and only 0.46 mg/l zinc were measured. The EPA aesthetic levels are 1.0 mg/l for copper and 5.0 mg/l for zinc. Both zinc and copper are essential minerals for good health - the FDA recommends a daily intake of 15 mg of zinc and 2 mg of copper.