The Hydro Life Hydroponics Twin RO Filtration System removes 99 percent of all contamination in water through reverse osmosis. First, water travels through the pre-filter, which is a sacrificial filter that removes heavy sediment from water, helping to extend the life of the KDF-85/Catalytic Carbon filter. Then, it moves to the KDF-85 filter which has Catalytic Carbon filtration to remove chlorine, chloramines, salts, heavy metals, sulfur, rust flakes and other sediment, plus KDF 85 to help prevent bacteria growth when the filter is not in use and extend the overall life of your hydroponic filter. Lastly the water passes through an RO membrane that rejects everything but water molecules, leaving you with a final product that has 99 percent reduction in parts per million contaminants in water. Reverse osmosis filtration helps stabilize pH levels, reduce mineral build-up and promote healthier flora.