Quick Answer
To choose the right horsepower for a shallow well pump, consider the static head, flow rate, and pump type. A general rule of thumb is to use 1-2 horsepower per 100 feet of static head. Calculate your load requirements carefully to avoid over- or under-sizing the pump.
Understanding Static Head and Flow Rate
Static head refers to the vertical distance between the water surface in the well and the pump’s discharge point. This can be broken down into two components: static lift (vertical distance) and friction loss (resistance to water flow through the pipes). When calculating the static head, consider the well depth, pipe length, and diameter to determine the total vertical distance the pump must lift the water. For example, if the well is 100 feet deep and the pipe is 50 feet long, the static head would be 150 feet.
Calculating Horsepower Requirements
To determine the horsepower requirement, multiply the flow rate (in gallons per minute, GPM) by the static head (in feet) and divide by 3960 (a conversion factor). This will give you the total head in pounds per square inch, which can then be used to determine the horsepower requirement. For example, if the flow rate is 10 GPM and the static head is 150 feet, the calculation would be: (10 GPM x 150 ft) / 3960 = 3.78 pounds per square inch. Based on the pump’s efficiency, this would translate to approximately 2-3 horsepower.
Selecting the Right Pump Type
When choosing the right pump type, consider the flow rate, static head, and well characteristics. Submersible pumps are suitable for shallow wells with high flow rates, while jet pumps are better suited for wells with low flow rates and high static heads. Centrifugal pumps are also an option for shallow wells, but may require additional support and maintenance. Always consult with a qualified professional to ensure the proper pump selection for your specific application.
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