Scheduling rehabilitation of pipes is essential for efficient maintenance and management of Water Distribution Systems. In reality, however, rehabilitation plans are more focused on subareas than on each pipe due to unpredictable variables: cut off time of water supply, number of traffic control times, and location of valves for example. This study determines rehabilitation priority order of subareas considering relative importance as well as deterioration of pipe. Water network is divided into several subareas according to valve locations and segments. Relative importance of pipes is included in the calculation process of rehabilitation priority order to consider hydraulic condition of the network. Then the relative importance of pipes is calculated on two failure simulations. The first simulation takes segments and unintended isolations to evaluate the relative importance according to the number of customers who are forced out of service when the segment is shut down. The second simulation develops Effect Index by considering abnormal condition which is produced when fluctuation of water causes sudden change of pressure. The decision making process adapts Weighted Utopian Approach by adding five weighting methods to get a result. The developed method provides practical results in the application to real networks. In this point, the model clearly has advantages over existing ones and can replace those in practice.