An efficient flash-purification system has been developed using a self-rotating nozzle powered by the feed-water flow. Where an electrically-powered, rotating nozzle distributes water droplets evenly in a flashing chamber to increase the evaporation rate, a self-rotating nozzle creates a continuous flow of droplets at the chamber wall by impact momentum effects. The aim of this study was to design and test a new self-rotating nozzle to improve the condensation rate in the flash-purifier. The device investigated employed a self-rotating nozzle of innovative design. The new system was constructed successfully and tested under conditions in which the vacuum and feed-water pressures, and the temperature were varied to maximize the condensation rate. Factorial design methodology showed that vacuum pressure was the most influential variable for condensation rate. The highest condensation rate achieved was 0.0748 ml/s, obtained from a combination of 2.0 bar-g feed-water pressure, vacuum pressure 0.3 bar-a and feed-water temperature 60 °C. Previous studies involved an electric rotating nozzle that generated 0.061 ml/s, but this study proved the efficiency of the self-rotating nozzle by producing a higher condensation rate.