The chapter starts by looking at the evolution of economic and financial aspects of drinking water and water treatment plants. Then examines the economic and financial procedures of drinking water. Accordingly, this chapter defining includes strategic content and assessment of environmental impacts for the water treatment plants. The demand analysis of the drinking water treatment plants discussed in detail under the economic and financial procedures. Includes, main parameters of demand projections and how to asses and different approaches to the evaluation of the demand. Then addressed estimation cost of water for drinking water treatment plant provides a selection of the various classification systems. Finally, the chapter presents an overview of treatment and sanitation costs for the infrastructure services.