RO and deionization modules are two different purification technologies. RO modules use the physical phenomenon of reverse osmosis, using pressure and a semipermeable membrane to reject impurities. Deionization modules use artificially produced resin to remove molecules based on positive or negative charge. The advantage of the RO module is that it removes a wide variety of impurities (ions, particles, organics, bacteria, salts, etc.) while the deionization module only removes ions. If ion removal is the only goal, deionization may be the better solution as it ensures constant ion removal on a higher base than a RO system. However, deionization is used to achieve Type 2 (or Type 1) water values, which typically also requires the removal of organics and other impurities. Therefore, a combination of both techniques is usually required.