In this work, reuse water networks have been modeled and optimized by the application of the Particle Swarm Optimization (PSO) method. From a built-in superstructure, which represents the whole possible configurations of the reuse water networks, a modified PSO method was proposed in order to lead with both discrete- and continuous-type variables in Non-Linear Programming (NLP) and Mixed Integer Non-Linear Programming (MINLP) models that represent water allocation problems. By introducing pinch analysis concepts, the improved PSO method has shown excellent performance in the optimality of reuse water network synthesis based on the minimization of freshwater flow rate, number of interconnections and annual total cost. PSO results were compared with those of the General Algebric Modeling System (GAMS) for all criteria, showing the flexibility and efficiency of the metaheuristic approach in solving water network reuse synthesis problems. © 2011 Elsevier B.V.