The informal market of purified water in Mexico grew in 2004 to 50% in some areas. Currently, the sale of bottled water is equivalent to 26.03 million l/year, 18.22 million in water jug and 7.81 million in individual water bottles. However, the commonwealth of Infiernillo, municipality of Arteaga, Michoacán, the market niche demand is unsatisfied; coupled to 2,600 habitants of the Colonies Pitireras and Morelos consume untreated water, that contain salts and these are extracted from the dam Infiernillo. The main objective of this research is to evaluate financially a water purification plant to meet quality and quantity of product demand in the study area. For this purpose, were evaluated the assessed the economic feasibility, the economic costs of production and the monetary benefits of commercialization. Financial indicators Net Present Value (NPV), Internal Rate of Return (IRR), Benefit Cost Ratio (B/C) and Net Benefit-Investment (K/N) are determined using a Microsoft Excel spreadsheet, the program analysis projects (ANPRO) and the Statistical Analysis Sistem package SAS. The economic information was obtained from an water purifying plant pre-feasibility study carried out in this community. The variables considered were costs of staff (509,400 pesos), raw and annually supplies (187,635 pesos), costs of fixed investment (309,543 pesos), deferred (35,087 pesos), annual costs (108,692 pesos) and revenue (3´077, 280 pesos). The results were going NPV = 6´745, 459.75 pesos; TIR = 44.15%; R B/C = 2.16 pesos and N/K = 21.73. To perform the analysis of sensitivity of total costs and total income, the project stand a decrease in the first of an increase of 20%, while in the second case it stand a decrease of 20%. However, the project shows viability.