In this chapter, after a brief review of the waterjet cutting process, we looked at the two different style pumps that are used in high pressure waterjet cutting: intensifier and direct drive and covered a few of the advantages of each pump style. The water pressurization process of an intensifier pump was detailed. We went through the different parts of an intensifier pump so that you will have a good idea what a sales person or technician is talking about when they refer to a part in a pump. We also discussed the On-Off valve and how it is used at the cutting head and in the pump. The abrasive feeding system was discussed, as well as the merits of a CNC-controlled abrasive metering system.