An above-ground well pump, often called a jet pump, works by using suction created by an impeller to draw water up from the well through a nozzle.
Here's a more detailed breakdown of the process:
Components and Location
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Location: The pump itself is located above ground, typically in the house, a basement, or a small structure called a well house. This is the key difference from submersible pumps.
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Jet Assembly: The heart of the jet pump system is the jet assembly, located either within the pump housing itself (shallow well jet pump) or down in the well (deep well jet pump).
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Suction Pipe: A pipe extends down into the well, acting as the conduit for water to be drawn upwards.
The Pumping Process
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Priming: The pump and suction pipe must initially be filled with water (primed) to start the process. This is because the pump relies on moving water, not air.
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Impeller Action: An electric motor powers an impeller (a rotating fan-like component) inside the pump.
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Creating a Vacuum: The spinning impeller forces water out of the pump, creating a vacuum or area of low pressure within the pump housing and the suction pipe.
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Drawing Water Up: This vacuum pressure then pulls water up from the well through the suction pipe. Atmospheric pressure pushing down on the water in the well helps force the water up the pipe.
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Nozzle and Venturi Effect: The jet assembly (containing a nozzle and a venturi) plays a crucial role. The nozzle constricts the flow of water, increasing its velocity. This high-speed water passes through the venturi, creating a further pressure drop (vacuum). This enhances the pump's ability to lift water, particularly in deep well applications.
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Pressure Tank and Switch: The water pumped from the well is delivered to a pressure tank in the house. When the pressure in the tank drops below a certain level (due to water usage), a pressure switch activates the pump, restarting the cycle. When the pressure in the tank reaches a set upper limit, the switch shuts off the pump.
Deep Well vs. Shallow Well Jet Pumps
The primary difference lies in the location of the jet assembly:
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Shallow Well Jet Pumps: These are used when the water table is relatively close to the surface (typically within 25 feet). The jet assembly is located within the pump housing above ground.
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Deep Well Jet Pumps: These are used when the water table is lower (beyond 25 feet). The jet assembly is located down in the well itself. This is necessary because shallow well jet pumps lack the suction power to lift water from great depths. These systems often use two pipes extending into the well: one to supply water to the jet and another to return the water to the pump.
Advantages and Disadvantages
| Feature | Advantages | Disadvantages |
|---|---|---|
| Location | Easier to access for maintenance and repairs. | Can be noisy. Requires priming. |
| Cost | Generally less expensive than submersible pumps. | Less efficient than submersible pumps, especially in deep well applications. |
| Depth | Suitable for both shallow and deep wells (with different pump configurations). | Limited lift capacity compared to submersible pumps. |
| Maintenance | Easier to diagnose and repair problems. | More prone to cavitation and other issues if not properly maintained. |
In summary, an above-ground well pump utilizes a combination of impeller action, vacuum creation, and a jet assembly to draw water from a well and deliver it to a pressure tank for household use.
