This work presents a practical method for the optimal economic design of looped water distribution systems. The method, here named PNL2000, is to determine the diameter of pipes and pumping piezometric levels, minimizing the total costs (investments and operation) of the water distribution system. The method is based on a non-linear programming technique, implemented with the Solver tool of the Microsoft Excel software. The applicability of the method was demonstrated in the design of a looped network within an urban water distribution system. The results showed that all the hydraulic constraints of the system were satisfied while minimizing the cost.