A borewell submersible is a long, slim vertical pump and motor that hangs inside a drilled borehole. An openwell submersible is a shorter horizontal unit that rests at the bottom of an open well, tank or sump. Both run fully under water, but they are built for different sources.
Borewell submersible pumps
The borehole diameter limits the pump's outside diameter, so these pumps are sold by bore size. Common nominal sizes are 3, 4, 6 and 8 inches, with larger sizes for high flows. The pump must fit inside the casing with clearance for the cable and cooling flow.
To build head in a narrow body, the pump stacks several impellers in stages. More stages give more head at the same flow. The motor sits below the pump, and water entering through the suction strainer flows past the motor and cools it.
Borewell motors are usually water-filled or oil-filled. Many Indian borewell motors are water-filled and rewindable, so a local workshop can rewind them after a failure. Impellers and diffusers may be noryl, stainless steel or bronze, depending on water quality and price level.
Openwell submersible pumps
Borewell pumps are usually installed with a non-return valve above the pump, a rising main and a safety rope. Make sure your installers know the maker's guidance on minimum submergence and maximum installation depth.
Openwell pumps are made for wide sources where diameter is not a constraint. They lie horizontally, often on a base or stand, with the motor and pump on one shaft. They usually have one or two stages and suit lower heads with higher flows than a borewell pump of similar power.
Because they sit at the bottom of the source, they need no priming and are not limited by suction lift. They are common for irrigation from open wells, building sumps and farm tanks.
What to check when buying
- For borewell pumps, confirm the bore diameter, the depth to the pumping water level and the total head at your flow.
- For openwell pumps, confirm the water depth, the risk of mud or debris and the delivery height.
- Ask whether the motor is water-filled or oil-filled, and whether local technicians in your market can repair it.
- Check the cable size and length for the installation depth, because voltage drop on long cables burns motors.
- Ask for sand handling limits if your water carries silt or sand.
- Ask what protection the control panel gives against dry running, overload and low voltage.
Indian makers build borewell pumpsets to IS 8034 and openwell pumpsets to IS 14220. If your market uses a different standard, put it in the specification. Our guide to writing a submersible pump specification covers this.
Next step
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