Once the capacity of pump needed is determined, the appropriate pump type should be chosen. There are many different types of pumps for water systems, and choosing the wrong one will lead to unsatisfactory water service.
There are basically two categories of pumps. Those used for lifting water from depths less than 22 to 25 feet and those used for lifting water from greater depths. Regardless of the pump type, however, each kind pulls water by suction from the well, and pushes the water by pressure into the distribution system. With this in mind, why then is there a distinction between deep and shallow wells?
In lifting water by suction all the pump is doing is removing
air from the inside of the pipe. As this occurs, the pressure inside
the pipe drops below its original pressure of 14.7 pounds, or
atmospheric pressure. Since the pressure acting on the water outside
the well is atmospheric, and the pressure above the water inside
the well is less than atmospheric, the water in the well rises as
a result of the difference in pressures.
As the pump continues to operate more and more air is removed from inside the well further lowering the pressure, until the atmospheric pressure finally forces the water in the well to the level of the pump. Assuming the pump in use is 100% efficient, the maximum height to which the atmospheric pressure could push the water is around 34 feet. Most real pumps, however, can only raise the water 15 to 28 feet. To be able to lift water from depths greater than 28 feet, the pump needs to be lowered until it is within 28 feet from the water level. Then it can lift the water to its level and push it to the surface. Shallow pumps are placed on the ground surface.
The following is a list of the different pump types. Examine some or all of them.
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