This report summarizes the results of ASHRAE Research Project, RP-450, "Water Flow Rate Limitations," completed by the Energy Research Laboratory at the University of Missouri-Kansas City. The purpose of the research project is to validate the available theoretical, experimental, and empirical data in the general area of water flow rate limitations. Information was sought, both nationally and internationally, on velocity limitations, as published by manufacturers', from previous investigations, from technical and trade literature, and from common use in practice.