Well water is essential to those who do not live in an area where public water systems are available. To get the water from the ground into a home, a deep well pump has to be used. The most common and efficient type of pump is a submersible pump.
Submersible Pump
Submersible pumps, or centrifugal pumps, are the obvious choice for a deep well system. As the name implies, this type of pump is fully submersed in the well. The appearance is that of a long tube that is inside a well casing. The pump is sealed in its own compartment, connected to the power source, an electric motor, by wires above ground.
Impellers
Submersible pumps work through the sealed electric motor, which spins a row of impellers. Each impeller pushes water through a diffuser into the one above it. In typical 4-inch pumps, each impeller adds 9 psi of pressure. If a pump has 10 stages, or 10 impellers, 90 psi of pressure will develop at the end point, or outlet. Pump capacity is determined by the impeller vane width and the number of impellers determines the pressure. Any increase in the well depth or the discharge pressure will minimize capacity.
Advantages
Submersible water pumps have obvious advantages such as being efficient and high in capacity. Maintenance required for the pumps are minimal. Usually, submersible pumps can work inside a well for 20 years without a problem. With wells that are 80 feet in depth or more, this type of pump is very economical.
Limitations
Impeller and diffuser tolerance is relatively small. Due to this intolerance, the pump cannot pump water that contains abrasives such as sand or gravel. This type of pump is water lubricated as well as water cooled, so if the pump is installed in a well that will pump dry, it may malfunction. A liquid level control can be installed on the pump to limit this type of malfunction. These pumps are also not suitable to pump water that may contain high concentrations of dissolved gases. The pump could get gas locked.
Choosing the Right Pump
Consumers need to be aware of their pumping needs before installing a submersible pump. Most submersible pumps are for wells with a minimum 4-inch side diameter. There are pumps for a smaller diameter but are much more expensive. Pump capacity and safe pumping capacity of the well should be two key factors for making a decision. Wells with a capacity capable of pumping 10 gallons per minute should not have a pump capable of pumping 15 gallons per minute. This is called over-pumping a well. In this scenario, the well and pump could be damaged.