
In this paper, we address the development of a global optimization procedure for the problem of designing a water distribution network, that satisfies tat specified flow demands as stated pressure head requirements. The proposed approach significantly improves upmon a previous method of Lahiouel et al. (2004) by way of adopting a simultaneous layout and pipe size otimization of water distributon networks. The necessity of a coupled solution of the layout and pipe sizing problem is shown. The method does not start with a predefined layout which includes all possible links; it is capable of designing a layout of predefined reliability, including tree-like and looped networks. The applicability of the model for optimization of pipe networks with predefined reliability is illustrated by testing the method against on benchmark example in the literature.