This paper describes the design and performance evaluation of swirl injectors which find application in the spray flash desalination system at low pressures and temperatures. Water was sprayed into the vaporizer through a swirl injector as fine droplets. The vaporizer was maintained at low pressure. The maximum flow rate was 1 l/s. The injector performance was determined at different feed water temperatures, vacuum and water injection pressures. The effects of injector dimensions and flow parameters on droplet production were studied and analyzed. Droplet size of 0.7-0.9 mm from the theory compared with the experiments estimates. From this study, it is established that the droplet diameter in the range of 0.7-0.9 mm is optimum for flashing.