Water system integration is one of the most efficient technologies for saving fresh water and reducing wastewater. However, the compact connection of water units often leads to insufficient resilience of a water system. In order to counteract the fluctuation of a real production process, a water network must be flexible. Two new concepts, maximum tolerance amount of a water unit (MTaWU) and tolerance amount of a water unit (TaWU) are introduced firstly in this paper. Based on these two concepts, the tolerance amount of a water network (TaWN) is proposed to quantify the resilience of a water network. A case study illustrates that these parameters are countable and straightforward. (C) 2008 Elsevier B.V. All rights reserved.