Compared to integration of water networks of a few plants separately, the integration of interplant water network can save more freshwater. This paper proposed an iterative method for design of interplant water network of multiple contaminants with an interplant water main by using the Concentration Potential Concepts. The key for design procedure of an interplant water network is to classify all processes into two groups based on reusing the water of the interplant water main or not. Then the design can be simplified into a design of a conventional single plant water integration with a central water main. An example is shown that the design procedure is simple and effective.