An under the counter water treatment system. Water from an outside supply source, such as a municipal water line, is provided to user's home. A prefilter to remove sediment, organic compounds, and certain pollutants is first provided. After the prefilter, the water enters a reverse osmosis system which includes an osmotic membrane. The reverse osmosis membrane filters out impurities and very small particles to provide highly purified water. The outflow of the reverse osmosis filter is stored in a water tank. Water is removed from the tank by releasing an appropriate valve when the user wishes to drink the water. When the water exits the tank, it passes through a mineral supplement which adds minerals to the water beneficial to human or animal consumption. It then passes through an electrolytic cell having a plurality of plates.