This paper presents a new methodology based on algorithms that includes the determination of optimal pressure surface, constraint programming and genetic algorithms to find an approximation to least cost design of water distribution network. REDES and EPANET programs are used for hydraulic simulation and two well known problems are solved finding solutions of less cost satisfying pressure constraints. This methodology is computationally much faster when compared with other algorithms used previously to solve this problem and good solution can be found. Furthermore is possible to optimize known solutions to find better solutions. The Hanoi network problem is tested and better solutions were found than those published previously in the literature.