Planning models for industrial water systems are needed to address future environmental regulations, increasing costs of freshwater, variability on the quality of the available freshwater source, and bottlenecks caused by expansion of the capacity plant, among other reasons. In this paper, we present a method to address an increase in plant capacity associated with new water-using units planned to be added through time and/or an increase in the mass load of existing water-using units. We compare this method with two ad-hoc alternatives, which exhibit good performance for the examples shown.