A holistic procedure GLOBAL for the global optimization of water distribution systems is presented. The procedure identifies an optimal tree layout for the network and augments it with loop forming links to assure reliability. Thus, the chosen optimal layout in judiciously subjected to various flow configurations to find an optimal flow division among pipes for the least cost diameter selection. Because the problem is nonconvex, two global search schemes, MULITIST ART and ANNEALING, both within the framework of procedure GLOBAL, are employed to permit a local optimum seeking method to migrate among various local minima. A modified Linear Programming Gradient (LPG) procedure is judiciously employed as local optimizer. An example problem from the literature is solved using the proposed procedure. The optimal solution has a cost very near to the theoretical limit for this problem and is significantly smaller than the ones reported by other researchers. / Master of Science