Determine the required borehole pump capacity.
Choosing the right pump is very important, because over and undersized pumps are very inefficient. They consume too much extra energy relative to the amount of water delivered. Pumps that are energy inefficient will have a shorter lifespan and more breakdowns. Selecting the right pump – even if it is more expensive in the short-term – is highly recommendable to get the maximum lifespan for the installation.
Here are the factors that you’ll need to consider.
- Pump application: What do you plan on doing with the water that you pump from your borehole? Different applications will require very different pumps.
- Flow rate and pressure: Based on your application, you will have an idea on what flow rate and pressure you are aiming for; that is the amount of water to be moved (or flow), and the pressure that must be generated to get the water to where it is needed.
- Borehole recharge rate: The water level in a borehole will drop as it is pumped out of the borehole, and rise as it is recharged. The borehole’s recharge rate is an important consideration when selecting a pump.
- Borehole diameter: Each borehole is drilled to a specific diameter. The diameter of the borehole will dictate the diameter of the submersible pump that will need to be used in the borehole. Always remember that a pump with a small diameter will generally need to have more stages or impellers than a pump with a larger diameter to achieve the same output.
- Pumping distance: The water's journey when being pumped will start underground and eventually be delivered to its endpoint by the pump. There are a few legs in this journey:
- From below-groundlevel to the top of the borehole i.e. the groundlevel (depth of the borehole)
- From the top of the borehole to the delivery point (horizontal distance)
- From the top of the borehole to the highest point the water will be pumped to (ground elevation)
- Total Dynamic Head (TDH): TDH considers the above ground elevation, pipe diameter, pipe length, standing water level and drawdown level.
- Pipe diameter: The size of the pipes in the installation is also very important consideration to achieve good results from your borehole. A small pipe diameter will create more friction than a larger-diameter pipe, so more pressure and hence more kilowatts will be required to account for the friction loss requireing a bigger pump capacity.
If the above factors are considered you will have the best chance of selecting a pump that will give you the best return on your borehole investment.