Pump Mechanics

How Do Well Pumps Work?

Most conventional well pumps work on a centrifugal basis - that is to say that they work by using their impellers' rotation to push water outward, and then upward through the well shaft. The motors in submersible well pumps are usually located below the pump itself. These motors, which are long and quite small in diameter, drive the pumps through relatively short shafts with seal sections which protect the motors from water damage.

Because the diameter of well is restrictive, the impellers have to be stacked on top of each other to exert enough pressure to force the water up through the pipe. This is why submersible well pumps are very long. A standard 4" submersible pump measures between 24" to 48" in length, 3.9" in diameter, and spins at 3600 rpm. The 3" submersible pump measures 2.9" in diameter and spins at about 8000 rpm. The number of impellers and diffusers a pump has, determines the head (or pressure) the pump exerts.

Pressure and Well Pumps

Pressure is usually stated in PSI (pounds per square inch) for example: 1 PSI = 2.31 feet. Pressure however, can also be stated as LIFT (as in vertical lift). When a submersible pump is turned on, it forces water through a pipe. If the pipe is in a vertical position, the pipe will have pressure throughout. The taller the pipe, the more pressure the pump needs to fill it. If the pipe is in a horizontal position, the pressure converts to flow and the only pressure being exerted is the friction the water produces as it passes along the pipe.