2.22. Optimum Rates of Flow. The question frequently arises as to whether one should have a small pipe or conduit with high velocity or a large pipe with low velocity. Although each installation should be analyzed carefully from the standpoint of initial cost, power requirement, noise level, and operating costs, the following general suggestions can be used as a guide.
Velocities of 4 to 6 ft per sec are usually best for water. Ten feet per second may be used if the system resistance is low. Where noise is not a problem, air systems may be designed for velocities of 1000 to 1500 ft per min. Velocities up to 2000 ft per min may be used in large pipes. The reader should realize that these values are general and that frequently values above or below these should or could be used