US Water Systems Gray & Black Filter Housings use a Double-O-Ring “Posi-Seal” design, so that 100% of the water is deionized. The standard DOE (Double Open End) cartridges can allow “blowby” and therefore small amounts of water is not deionized, resulting in poor water quality. US Water Systems offers both Posi-Seal, and DOE DI Cartridges in most sizes. We also have DI resins from Thermax, ResinTech, and others. Talk to one of our Master Water Specialists to get the proper cartridges, parts or DI resin you need.
US Water offers the highest quality high-purity deionization or DI resin, semiconductor grade DI resin and color-changing DI resin. In our experience, the highest capacity and best resin is the Resintech Semiconductor Resin. People with aquariums and reefkeeping systems like the color-changing DI resin, but remember, it does not have the same capacity as the semiconductor-grade resin. That means that you won't get as many gallons out of the color-changing resin as you will from the semiconductor grade resin.