Pure drinking water is one of the major concerns all over the world as 97% of water resource is not drinkable due to high salinity. Fresh drinking water is one of the indispensable needs for human being as well as other living creatures' survival. Like many others countries in the world, Bangladesh is one of the developing countries that has not been able to overcome the freshwater crisis yet, especially for its people of the coastal regions. To assist the rural or isolated communities by fulfilling their pure drinking water demand, a small scale brackish water reverse osmosis purification system assisted by solar photovoltaic (PV) energy as the renewable energy source has been proposed in this work. It has been revealed that solar PV source serves the best for a small scale power generation for the rural or remote region and reverse osmosis process is the most economical system for brackish water purification. After a thorough experimental investigation and analysis, it was found that the system fulfilled the national and international standard of pure drinking water, where 0.19BDT/litre (0.0022USD/litre) has been achieved as the most cost-efficient outcome of the water purification system. Other existing pure drinking water systems that offers around 1.0BDT/litre (0.013USD/litre) as the retail price in Bangladesh at present.