This paper presents an optimization formulation for designing residential water networks involving harvested rainwater and reclaimed wastewater. The design problem is posed as a multi-objective optimization formulation that seeks to balance the objectives of total annualized cost, fresh water consumption, and environmental impact. A life cycle assessment approach is undertaken for estimating the environmental impact. The seasonal dependence of the rainwater is considered in the optimization model. The design approach is applied to a case study for the city of Morelia in Mexico. The results show that significant economic, fresh water consumption, and environmental benefits can be obtained as a result of the proposed approach. (C) 2015 Elsevier Ltd. All rights reserved.