Water distribution system GIS data meets a variety of needs including automated mapping, facilities management, work order processing, meter records and billings, and emergency planning. Detailed hydrant, valve fitting, pipe topology, and attribute data typically exceeds the level of detail required for hydraulic and water quality modeling of distribution systems. This paper presents an ArcView GIS application that processes detailed water system data in a systematic manner, resulting in a data set that supports water system model construction. The processes completed by this ArcView GIS "generalization" application include Reduction: Reduces excessive granularity in the detailed infrastructure data by dissolving nodes representing valves, hydrant lead fittings, etc. Skeletonization: Deletes small diameter pipes Trim: Deletes dead-end mains such as hydrant leads