This paper presents a mathematical model for the inter-plant water integration of an industrial complex that consists of a number of process plants. Opportunities for water reuse/recycle across plants are exploited. In particular, a novel integration scheme is proposed, where central and decentralized water mains are placed to interconnect the water-using units of the individual plants. The principal advantage of using water mains is to improve the overall network practicability. The model formulation is based on a series of superstructures, and the design problem is optimized according to two objectives that include the minimization of fresh water consumption and total annualized cost. An example is solved to illustrate the proposed integration scheme and approach. (C) 2010 Elsevier Ltd. All rights reserved.