The need for efficient pipe networks for urban water supply and drainage is introduced and discussed in the context of global sustainable development. The role of computer based analysis and design tools in the planning and operation of such systems is described, with the way in which these tools can help to minimize use of resources, energy and water losses being explained. In particular, numerical techniques such as Genetic Algorithms, which are based on the principles of natural evolution, are found to be particularly effective in dealing with the large, complex systems that typify urban water distribution networks. These evolutionary techniques are introduced and discussed, and several applications of the techniques to the development of efficient water systems are described. A case study on the use of these techniques in the calibration of an accurate mathematical model of an urban water distribution system is included.