The effective changes in a water-using process can reduce freshwater consumption and wastewater generation. The main effects of process changes include the increment of limiting inlet/outlet concentrations of water-using processes and the reduction of the contaminant load of those processes. Because the water pinch of a water system is the bottleneck to limit the freshwater consumption, in this paper a water pinch diagram is used to explore the impact of process changes oil the pinch point. Process changes which can move the pinch point upward and/or leftward can reduce freshwater consumption in the system. To further save freshwater in a water system, a process change which can increase limiting concentrations should be executed to an across-pinch process, and a process change which can reduce contaminant load should be executed below the pinch.