Abstract: Water substantially free of pyrogens and microorganisms that meets the requirements of United States Pharmacopoeia Standard USP XX Water for Injection is produced by processing drinking quality water through a filtration step adapted to remove organic contaminants and impurities that degrade downstream seperation membranes, a reverse osmosis step to remove dissolved solids, pyrogens, microorganisms and chemical contamination, a deionization step to further remove dissolved solids, and an ultrafiltration step to remove pyrogens. A sterile filter to remove microorganisms increases the water quality to USP XX Sterile Water for Injection. Means are provided to periodically remove accumulated chemical contaminants, pyrogens and microorganisms from the reverse osmosis apparatus, the deionization apparatus and the ultrafiltration apparatus. The sterile water can be admixed with a sterile concentrate composition to produce a sterile dilute solution that can be packaged under sterile conditions.