Design of water distribution networks is traditionally based on trial-and-approach in which the designer assumes, based on experience and judgment, sizes of different elements and successively modifies them until a network with satisfactory hydraulic performance is obtained. This text covers essential hydraulic, economic optimization principles. Theory is developed gradually for optimal design of simple, single-source branched networks subjected to single loading to complex, multiple-source looped net works subjected to multiple loading. Describes strengthening and expansion of existing networks and also reliability-based design.