a compact, portable, single unit apparatus has been evaluated for purification of sea water, pond water, and human urine. the process is based on the reverse osmosis procedure with a combination of pure bleached cotton, cellulose, and activated carbon filters. the results indicate that brackish, polluted water can be purified by a single passage through this system, as demonstrated by considerable reduction or complete elimination of ions, metal content, and organic matter present in the source of water. the water obtained is clear, colorless, odorless, sterile, non-pyrogenic, does not contain antimicrobial agents or other added substances, and appears to satisfy the criteria for usp grade water for injection except for the limits on total solids. the remaining solids are sodium and chloride ions which are commonly added to injectable water prior to clinical use. this water purification process could be useful in many non-military situations, such as at disaster sites, on off-shore drillings platforms, on commercial and pleasure boats, and at other locations where pure water is needed but not available