Once the basic requirements are met and the liquid characteristics are known, the pump selection can begin.  Pumps are generally divided into two basic categories: kinetic energy pumps (of which type are centrifugal pumps) and positive displacement (PD) pumps.  According to the U.S. Department of Commerce, about 70 percent of total pump sales are for kinetic pumps and the remaining 30 percent are for positive displacement pumps.  When choosing a pump, choose between a centrifugal pump and a positive displacement pump which is more suitable for your needs.