A new network structure is proposed in which internal water mains are utilized. The structure simplifies the piping network, as well as the operation and control of large plants involving many water-using processes, such as petrochemical or chemical complexes. It is accompanied by a new design procedure to generate networks having internal water mains, limited to a single contaminant with water reuse permitted, involving mass balances only and simple strategies for water minimization. Emphasis is placed on positioning of the internal water mains to simplify the networks., with the first internal main usually positioned at the pinch concentration. Strategies to reduce water consumption, through the use of local pipes and outlet concentration shifts, are discussed.