A good contractor needs to consider what type of pump is to be used in the borehole as well as its size and the casing and screen diameters needed to house it. Relatively low-yield boreholes intended for hand pumps with submerged pistons are rarely more than 30 meters deep and need not be of large diameter (4 inches can be enough).

A Submersible pump is designed such that it can be submerged into the water and pump. The submersible pump is a centrifugal pump, its impellers are designed to throw water outwards. The impeller blades are backward curve type. Several impellers are connected to a single shaft, which is driven by an induction motor. The water enters through the eye of the impellers. It is then thrown out radially due to the centrifugal force involved. This movement gives water both kinetic and pressure energy. This water is then passed to the next impeller’s stages via a diffuser. When the water passes each impeller, the pressure gain is multiplied at each stage. The water is then passed through a non-slam check valve. This addresses the concern of high-altitude pumping called the water hammer. The working methodology of the pump makes it quite efficient, practical, and reliable for several applications. The popularity of submersible pumps has grown since the 1960s and industries seek several benefits because of their submersible capabilities. Their popularity and ease of use have made them an inevitable part of water pumping.

What factors should you consider before choosing the right submersible pump?

All the submersible pumps work with the same mechanism and operate on the same principle. But these pumps are designed differently depending upon the usage and purpose. Each of the pumps varies in terms of technical details and their applications. They also come in several designs like Borehole Submersible Pumps, Openwell Submersible Pumps, Horizontal Openwell pumps, vertical multistage pumps, deep well submersible, and much more. Before buying a submersible, you’ll need to compare the brands, the models, and other relevant factors according to your usage. We have carefully curated a list of factors that will help you to select the right submersible pump –

1. Type of Water
Before buying a submersible pump, the most important thing to know is the type of water you are looking to pump. Depending upon the water type and location the specification of the submersible pumps change –

• Submersible pump for clear water – If you are looking to collect clean water like rain and looking to pump it for storage, then a narrow submersible pump with a maximum grain diameter of 5mm will be the ideal choice. You’ll also need to check how much dirt will be pumped along with the water.
• Submersible pump for dirty water – If the water you look to pump contains a lot of dirt, then you’ll need a pump ideal for dirty waters. These pumps should be able to function correctly even with mud and dirt particles. These pumps can be used to clean sewage and septic systems. Grain size is one of the most important factors to consider before buying a submersible pump for dirty water. The desired gain diameter that you are looking for is 10 to 20 mm.
• Submersible pumps for wells – These pumps are often used to pump water from home plumbing systems. Not all pumps are suited for very deep groundwater pumping, thus, submersible pumps are used for pumping water from deep wells.
• Submersible Pumps for Gardens Pond – A submersible pump is needed to run a fountain or manage a flowing stream. The pumps can be directly placed into the water. There are different types of pumps available for freshwater and saltwater.

2. Float Switch and Flow Switch
Another important factor to check upon before purchasing a submersible pump is a float switch. This switch is used to control the pump based on the water level. In several instances there is no water in the area that you are pumping water from, then this switch is used to stop the pumping. Running a submersible pump with water can cause some serious damage, a float switch will automatically turn it off when the water stoops down to a lower level. A flow switch is used to decide how much water will pass via the pump at a given point in time. They are of two types – vertical switches, used in smaller submersible pumps often come in 10-inch diameter and tethered switch, used to activate the pump and is available in 14-inch diameter.

3. Discharge Height
Generally, submersible pumps are used to pump water from lower to higher locations. This is the discharge height. It is used to determine whether the water will reach the designated height or not. If you want to pump water from the rain barrel to another container then your discharge height will be quite less. But if you look to pump water from the basement to a significantly higher place then you would need a higher discharge height.

4. Discharge Rate
The discharge rate defines how much water the submersible can pump per hour or minute. This is also known as the pump’s power level. If you are looking to pump water out of the barrel, then a 250-500 per hour power level will be sufficient for this application. If you want to pump water out from a basement level, then you’ll need a submersible with a high-power level i.e., with a discharge rate of 1 – 2 gallons per hour.

5. Back-up System
Submersible pumps are powered by electrical voltage. Thus, it is very important to get a pump with a power backup to avoid the severe flooding and cleaning process which largely depends on electrical pumps. A pump with the battery will provide power and make it last through the long hour contingency situations.

6. Cooling System
Submersible motors are either oil-filled or water-filled. For the water-filled motors, the coolant is water and can be refilled repeatedly. But in the case of the oil-filled motor, there is no coolant, this can increase chances of wear and tear of the motor and damage. This is the reason, you’ll find water-filled pumps costlier than oil-filled pumps but choose wisely.

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7. Suction Depth
When the water is pumped, its water level drops. Sometimes the suction assembly is not even covered entirely with water, this causes air to get in and stops the pumps from doing their job, which is not sucked, this is called the suction depth. It is the water level at which the pump operates.

8. Outlet Size
The submersible pump needs to be connected to an outlet pipe through which the water is pushed. They are available in several sizes and can be used for different applications. The outlet size should match the size of the pipe connected to the storage tanks. The outlet size diameter is generally measured in inches and mm.

9. Bore-well Size
This is the size of the hole to place the submersible, often called the borewell. You can check the diameter of the pump and then dig the borewell. The bigger the pump, the bigger the borewell. You can also fit a small submersible into a larger borewell but not vice versa.

Certain types of hand-pump can be fitted with counterweighted operating handles, to make drawing from deeper water levels less exhausting (mainly for women in developing countries).

Mechanical reduction of the submerged piston stroke can make drawing water easier, but as less water is drawn by each stroke of the pump, filling a container takes longer. Shallow boreholes often tap weathered zone aquifers above hard, impervious clays or bedrock (such as granite). The standard practice is to place the pump inlet slightly above the upper end of the screen.

For hand pumps, this does not matter much, the pump inlet could be lowered into the upper part of the open hole/sump (by attaching extra pipes) if there is a significant fall of static water level in the borehole because of prolonged drought.

More powerful types of pumps, such as electric submersibles and rotary positive displacement pumps, must always be installed inside protective plain casing: screens are not appropriate for this purpose.

The internal diameter of the pump chamber should be at least 5 centimetres (about 2 inches) greater than the external diameter of the pump.