A graphical approach for the design of heat-integrated water systems has been proposed to improve conceptual understanding for implications of heat recovery in water systems, as well as to provide systematic design guidelines for selecting most appropriate integrated options in practice. The developed design method aims to fully exploit water reuse potentials between water-using operations, and simultaneously to minimise any potential degradation of energy recovery resulted from water reuse. Graphical representations of heat-integrated water systems and their manipulation have been applied to investigate systematically design interactions, impacts associated with stream merging and splitting, and influences of non-isothermal mixing on heat recovery. Water Energy Balance Diagram has been developed to improve energy recovery in water reuse network. Energy-efficient and cost-effective configuration for heat recovery has been identified, using improved Separate System Approach. The proposed approach significantly reduces both water and energy requirements for single-contaminant water systems. (C) 2009 Elsevier Ltd. All rights reserved.