Each pump lifts water from Lake Roosevelt up through a 12 foot diameter discharge pipe to the feeder canal above. For most of their length the discharge pipes are buried in the rocky cliff to the west but at the top of the hill they emerge and can be seen as 12 silver pipes leading to the headworks of the feeder canal. The original pumps can supply water to the feeder canal at a rate of 1,600 cubic feet of water a second while the newer units can supply 2,000 cubic feet of water a second. They also have the advantage of being reversible. During times of peak power need the new pumps can be reversed thus turning them into generators.
Water flows back down through the outlet pipes, through the generators and into Lake Roosevelt.
When opearting in this mode each pump can produce 50 megawatts of electrical power. The original pump-only units get their power from direct connections to generators in the Dam's left powerhouse. One generator can supply enough power to run two pumps. Therefore, during the pumping season, three left powerhouse generators are dedicated to the task of powering six pumps. This allows them to draw power from the grid when operating as pumps and supply power to the grid when opearting as generators.