Desalination of water is essential to supply sufficient good quality water to remote areas to satisfy various needs. Saudi Arabia has enormous amount of deep water and the underground water in many areas of this country is so brackish that it requires extensive pre-treatment. In order to utilise inland reserves of brackish water by the local inhabitants, the Energy Research Institute (ERI) of King Abdulaziz City for Science and Technology (KACST) installed a Photovoltaic (PV) powered water desalination Reverse Osmosis (R.O) plant at Riyadh, Saudi Arabia. The reject brine rate from this plant is very high. Due to the inherent advantages of solar still assemblies, for instance; simple to construct and maintain using locally available material, and high technical feasibility in remote areas, a solar still plant capacity of 5.8 cubic meter distillate per day is proposed to couple with the existing PV-RO plant in order to utilise most of the reject brine instead of throwing on the ground. The estimated cost of product water obtained through this design is found to be Saudi Riyal 1.9 (US$0.50) per cubic meter. The proposed design of the solar still assemblies can be applied to configure a 100% solar powered desalination system for any location and quality of brackish water.