The common methods of desalination saltwater for production of fresh water by distillation, reverse osmosis and electrodialysis are intensive energy techniques. However, in remote and areas. the desalination needs not exceed a few cubic meters per day. This decentralised demand favours. local water production by developing other desalination processes, especially those using renewable or recovered energy (solar, geothermal. etc.). Solar desalination process C, 9 is one of these methods used to resolve the scarcity of fresh water. Several reviews have been published by different authors. Small production systems as solar stills can be used if fresh water demand is low and the land is available at low cost. To supply the population of remote and lands of South Algeria with drinkable water, solar distillation of brackish waters is recommended. It satisfies some of theses demands. Solar stills are used to produce fresh water from brackish water by directly utilising sunshine. These stills represent the best technical solution to supply remote villages or settlements in South Algeria with fresh water without depending on high-tech and skills. The production capacity indicates a possible daily production of far more than 151/m(2)d. Therefore, the still has a place in the upper range of known comparable products with regard to production output. This depends on the material used and the price of the solar stills and their accessories. The best working temperature solves most problems. Small, modular high-performance stills with features like the possibility of decentralised use, less maintenance and robust construction can help to reduce fresh water scarcity. The recent development of stills based on new concepts and heat recovery has been successful. The technical optimization is still in process today, it aims to improvement of the efficiency of these distillers. In our research work, a plant for brackish water distillation by directly sunshine and heat recovery was constructed and investigated experimentally and theoretically in South Algeria. This study aims the improvement of the performance of this solar distillation plant. conducted under the actual insulation, for brackish underground geothermal water desalination.