This paper discusses how water distribution system computer models can be used to assess and improve the effectiveness of conventional flushing programs. Using the model, flow rates for each hydrant are simulated to predict pipeline flow velocities. Model output is then analyzed to identify pipeline segments that do not achieve the target flushing velocity. The target flushing velocity can vary from system to system and may depend on the flushing program objectives. The length of pipeline segments that do not achieve the desired flushing velocity compared to the total length of pipeline in the system provides an estimate of the efficiency of the conventional hydrant flushing program. The model can also be used to develop specific procedures for improving the flushing effectiveness by increasing the flow velocity in areas of the system that would not otherwise achieve the desired flushing velocity. For example, the model can predict how opening additional hydrants and/or strategically closing valves could increase flow velocities in certain pipes. Directional or other special flushing procedures can be implemented based on the model results, to improve flushing effectiveness for specific areas of the system. The primary advantage of this system flushing approach is that the utility only performs more costly flushing techniques in areas of the system where they are required to achieve flushing velocity goals. In addition to optimizing pipeline flow velocities to maximize the flushing program effectiveness, the hydraulic model can be used to predict minimum system pressures that will occur during the flushing event, to help ensure that minimum system pressure requirements are maintained, and to establish key pressure monitoring locations. In addition, the model can be used to help establish flushing routes based on normal flow directions. Includes 3 references, table, figures.