Pump rod of fiberglass, wood or steel connects plunger of pump to valves in cylinder and brings about actual pumping action.
There is a check valve at the bottom of the cylinder and simular valve in the plunger. Water flows into the cylinder through the check valve while the plunger is making its up-stroke. On the down stroke, water is held in the cylinder by the check valve and the plunger descends to bottom while water passes through valve in plunger.
On the next up stroke, the valve in the plunger closes and water above it is raised up into the drop pipe. At the same time, the check valve opens and the cylinder fills with water again. With each up stroke the pump, the plunger forces a cylinder full of water into the drop pipe and out to the discharge tank.