An above ground well pump draws water from the ground by creating a suction that pulls the water upwards.
Above ground well pumps, particularly types like jet pumps, operate by creating a vacuum or low-pressure area within the suction pipe that extends down into the well. The higher atmospheric pressure exerted on the water level in the well then pushes the water up the pipe towards the pump.
The Basic Mechanism
The core process relies on the principle of pressure difference:
- Equipped with a Suction Pipe: The pump is connected to a pipe that goes down into the well water. This pipe must be primed (filled with water) initially for the pump to work correctly, especially in non-jet centrifugal pumps.
- Creating a Vacuum: The pump's motor drives an impeller (in centrifugal pumps) or uses a specific mechanism (like a jet assembly in jet pumps) to move air and water out of the pump casing and discharge pipe. This action significantly lowers the air pressure inside the suction pipe and pump casing.
- Pulling Water Up Through a Nozzle: As mentioned in the reference, the pump pulls water up through a nozzle by creating a vacuum. In jet pumps, a portion of the discharged water is sent back down a separate pipe to a jet assembly at the well's water level. This water passes through a nozzle at high speed, creating a low-pressure zone (the vacuum effect) that draws well water into the suction pipe.
- Atmospheric Pressure Does the Work: The weight of the atmosphere pushes down on the water surface in the well. Since the pressure inside the suction pipe is much lower (due to the vacuum), this atmospheric pressure forces the water up the pipe and into the pump.
- Discharge: The pump then moves this water out through the discharge pipe towards your home or storage tank.
Here's a simple breakdown of the process:
- Pump lowers pressure in pipe.
- Atmospheric pressure pushes water up.
- Water enters pump.
- Pump pushes water towards destination.
Types and Considerations
While the fundamental suction principle is similar, above ground well pumps often fall into categories based on how they achieve suction:
- Shallow Well Jet Pumps: Typically used for wells up to 25 feet deep. The pump unit is above ground, and the jet assembly is usually built into the pump itself.
- Deep Well Jet Pumps: Used for wells deeper than 25 feet. The pump unit is above ground, but the jet assembly is located down in the well, often submerged just below the water level. As noted in the reference, deep-well jet pumps are usually quite powerful as a good amount of energy is needed to pull the water up. The extra power is needed to recirculate water down to the jet assembly and create enough suction from greater depths.
| Component | Function |
|---|---|
| Motor | Powers the pump's mechanism |
| Pump Casing | Houses the impeller or jet assembly |
| Suction Pipe | Connects pump to water in the well |
| Discharge Pipe | Carries water from pump to destination |
| Jet Assembly* | Creates vacuum using a nozzle/venturi effect |
| Pressure Switch | Starts/stops pump based on system pressure |
*Applicable mainly to jet pumps.
Above ground pumps are popular due to easier access for maintenance compared to submersible pumps, but they are limited by the suction lift height, generally unable to effectively pull water from depths much greater than 25 feet using simple suction alone. Jet pumps overcome this limitation for deeper wells by using the jet assembly in the well.
