KDF is a proven and patented method of removing bacteria, chlorine, chloramines, fungus, iron, most heavy metals, hydrogen sulfide, algae and more from your water. It's made of 50% pure zinc and 50% pure copper. When water is exposed the KDF produces a reaction that turns free chlorine into simple chlorides. Other harmful contaminates are rendered harmless. KDF can remove 95% or more of chlorine. The electrolytic field forms hydroxyl and peroxide radicals and inhibits microorganisms. Because the zinc and copper ions tend to reattach to the media, these filters meet FDA and EPA standards. KDF won't remove minerals and is best used in combination with other filters for really effective filtration.
GAC, or Granulated Active Carbon, is very good at reducing or eliminating bad tastes and odors. It gets rid of many contaminates but not as many sub-micron particles. It doesn't remove minerals and is an ideal post filter used in combination systems.