A new time-purity two-dimensional water-using diagram was presented to synthesize water network for batch processes. In the diagram y-axis was water purity and the x-axis was time.Design rules with or without storage tank were presented respectively.The diagram could clearly describe water-using batch processes.The method firstly determined the pinch point and the minimum utility targets of the batch processes by the water cascade analysis technology

then synthesized the water network by using the diagram and rules

and then determined the number and volume of storage tanks for batch processes with storage tanks

and lastly described the synthesized optimum water network by the time-water network diagram.The influence of the water network by the flowrate demand of a water-using process was also discussed.Calculation of two literature examples showed that the method was easy

effective and efficient.