An apparatus and methods for producing purified drinking water are disclosed. A hand pump is used in a closed system to generate pressure sufficient to pass the untreated water through a system of filters and a reverse osmosis membrane. The system preferably includes an ultrafiltration filter. The resulting water is substantially pure, being free of bacteria and having a significant amount of minerals and salts removed to make it safe for drinking. The system can produce enough potable water to supply the daily needs for a small village.