The ZeroWater ZD-018 Filtered Refrigerator Water Dispenser uses a patented five stage dual ion exchange filter system. This water filter has the advantage of purifying water right in the container. No need of installing big water filter systems that occupy space. This pitcher is the easiest way to purify water pour the water in the pitcher, it then uses the patented five stage system to purify it. Pour out the water and drink it right then. It can fill up to 23 cups of water at a time and that is the largest capacity water filter in the market. It comes along with a built-in TDS meter that constantly tests for the purity of water. It removes chlorine, dust, iron, sediments, silt, rust, sand, lead, and all the dissolved salts. The ZeroWater ZD-018 Filtered Refrigerator Water Dispenser is the only filter that meets the FDA required TDS levels of purified water, 000-010ppm.