Submersible Borehole Pumps

Submersible pumps are used for extracting groundwater from boreholes and deep wells, where clean water is found that usually requires no treatment. While traditional self-priming pumps and domestic waterworks can only operate up to a depth of 8 meters, beyond which suction is not possible due to physical principles, submersible borehole pumps can draw both potable and utility water from depths of up to 150 meters. They are submerged in the water, which they then draw in and push through the water pipes to the points of use. Thanks to high-quality materials and workmanship, borehole pumps are designed for long-term submersion in both horizontal and vertical positions. They are also suitable for use in narrow spaces where it is not possible to install submersible well pumps. The functionality of submersible borehole pumps with a 100 mm diameter is the same as that of pumps with a 74 mm or 130 mm diameter.

A well-chosen pump will ensure a constant supply of water from your own source with silent and almost maintenance-free operation for many years. You can also easily extend its lifespan with proper care. Another advantage is the easy installation of a submersible borehole pump.

Preparing the Borehole for Water Pumping

After constructing your own water borehole, nothing stands in the way of starting to pump drinking water from it. However, before you begin selecting the best submersible borehole pump, it is necessary to prepare the borehole so that the pump can function optimally.

Borehole Cleanliness

Submersible water pumps for boreholes are designed for pumping clean water, so it is essential to ensure that there is not an excessive amount of sandy material or other abrasive substances in the borehole. The acceptable amount of these particles is specified by the manufacturer for each submersible pump, and for high-quality Grundfos borehole pumps, these values range from 50 to 150 g/m³. A higher concentration of solid particles in the water leads to faster wear of the submersible pump and thus shortens its lifespan.

To achieve the highest quality water from your borehole, we recommend installing a domestic cold water filter, which protects appliances from sand and dirt deposits. For new or contaminated boreholes, it is necessary to clean them, which is recommended to be repeated every 4 to 7 years depending on the borehole conditions.

Presence of Air in the Borehole

The presence of gas/air in the water reduces the performance of the borehole pump and can even cause it to stop completely. An effective protection is the installation of a special casing to increase the pressure around the submersible borehole pump for drinking water.

Borehole Yield

The yield of the borehole directly affects the amount of water that can be pumped from it. To ensure the proper functioning of the submersible borehole pump, it is necessary to ensure sufficient water flow around the pump for cooling. Excessive depletion of the borehole can lead to the pump running dry, which can irreparably damage the submersible pump. Grundfos SQ and SQE submersible borehole pumps have built-in dry run protection and can stop pumping in time if there is a lack of water in the borehole. Frequent switching on and off of the pump shortens its lifespan, so it is advisable to avoid this problem during the initial borehole preparation.

If the submersible water pump is placed in dug wells and tanks where there is not sufficient depth, it is essential to ensure cooling by the flow of surrounding water for its trouble-free operation. The same effect can be achieved by installing a cooling jacket.

Which Submersible Borehole Pump to Choose?

Recommendations from family and friends are always the best advertisement, but boreholes can differ from each other. Therefore, it is important to choose a submersible pump that matches the conditions of your borehole. An improperly chosen submersible pump will cost you higher operating expenses and a shorter pump lifespan. In the worst case, it can even lead to the devaluation of the entire borehole. The same applies to the incorrect installation of a submersible borehole pump.

How to choose a submersible pump for drinking water boreholes?

Pump Diameter

The diameter of the submersible pump must be smaller than the diameter of the borehole itself. There should be at least a 10 mm gap between the pump casing and the borehole wall, ensuring sufficient water flow and exchange for cooling the pump and providing protection against mechanical damage to the submersible pump. There is a wide range of submersible pumps for narrow boreholes, and you can also find submersible pumps with a small diameter (starting from a diameter of 74 mm).

Required Flow Rate

Another important parameter for selecting a submersible borehole pump is the anticipated amount of water you want to pump, known as the flow rate. Ideally, its value should be around 3 m³/h. The flow rate of a properly selected pump should be as close as possible to the point of best (peak) efficiency, while the pump should operate minimally at maximum flow. If the flow rate requirement falls between two models, choose the one that better suits the other parameters.

Pump Head

The pump head indicates the distance to which the submersible pump must deliver the water. This value determines the pressure needed to get the required amount of water to the highest point of use. When selecting a submersible borehole pump, it is true that the greater the distance, the greater the pressure the pump must develop. The pump head is simply calculated as the sum of the vertical and horizontal distances from the water source (pump) to the points of use. Horizontal meters are divided by a coefficient of 10 (less force is needed to deliver the same amount of water than in the case of vertical meters).

An example of pump head calculation is shown in the image.

Depth of Submersible Pump Installation in the Borehole

The submersible borehole pump must be selected with regard to the depth at which it will be installed. When placed at a greater submersion depth, the water column exerts higher pressure on the submersible pump, affecting its seal. If the submersible pump is placed below the maximum submersion depth, the seal may not withstand such pressure, leading to damage to the internal parts of the pump by seeped water.

Information on the correct installation depth can be found in the technical sheet of the submersible pump.

Built-in Features and Accessories

Ideally, choose a submersible pump that, once properly installed, will work as efficiently as possible and ensure that no problems arise for you. The simplest way to achieve this is by purchasing a complete set that includes everything you need.

Suitable solutions include submersible borehole pumps with a frequency converter Grundfos SQ and SQE, which offer many other features, or submersible borehole pumps Wilo TWU and TWI. These submersible pumps also include protective elements (dry run protection, protection against voltage fluctuations, etc.), so you do not need to purchase additional accessories.