Hello David, One possible reason is that the model is not calibrated to the system. In such a case, you might be seeing pressures that are higher than you would normally see. For instance, if the roughness values in the pipes are adjusted to better reflect the system, you may see pressures decrease during the fire flow run. With lower pressures, the pressure constraint will be reached sooner and the fire flow will be lower. You may also want to see if there may be a pipe or valve setting that may be different in the field than what you see in the model. A partially closed valve in the field that is not represented in the model might make the results different as well. The following link has information on Darwin Calibrator, a tool in WaterGEMS that can be used to help with the calibration process: http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/using-darwin-calibrator Regards, Scott
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