Optimization of water networks can always reduce freshwater consumption and wastewater discharge via finding the potential opportunity for direct/indirect water reuse/recycling. In most cases, however, some treatment units (i.e., filtration, ion exchange) that are known to have two outlet streams, with both the outlet streams commonly reused in industry, were often modeled as single outlet units in previous works, and the published double outlet models cannot describe those units very well. Thus, in this paper, a new double outlet model was proposed. Also, such a model was used to construct the water network superstructure, in which both the outlet streams of such a double outlet treatment unit can be connected with process units, other treatment units, or the discharge, aiming to find the potential for reusing the outlets of such a treatment unit. In particular, a multiple, staged system consisting of such double outlet units that is widely adopted in industry was incorporated in the network, and the superstructure of that system was specially developed. Also, the discussion of double outlet units performing as pretreatment or distributed treatment units was also carried out. All those investigations were demonstrated through a case study of a practical water network in a power plant, and the results show that the proposed approach is applicable and effective.