This paper is a resume of the author’s involvement with variable speed pumps as applied to hot and chilled water systems. It describes the accumulation of knowledge about variable speed pumping equipment and design of these water systems for variable speed operation. The basis of this paper is practical experience, not hypothetical conjecture; it reveals some unforseen changes in the design of water systems. Also, this paper provides information on the energy savings and ease of operation of variable speed pumping systems.Units: I-P