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Types of Pumps Used in Water Distribution

Potable water is one of the greatest natural resources on the planet. Every human, plant an animal on Earth needs water. At one time, potable water wasn't portable. Human settlement depended on the placement of water. So every town sprang up around a common well, stream or river. But with the invention of pumps, mankind was able to spread out and bring plenty of water to areas that would otherwise simply depend on rain.

Positive Displacement Pumps
- We've all seen the Old West movies, where people got their water from a hand pump next to a trough. Those old-fashioned hand pumps, a staple of early America, are positive displacement pumps. The handle pushes a piston inside the pump. When the pump handle is pulled, the piston pulls the water into the piston case through a valve. When the handle is pushed, the piston pushes the water out through another valve and, ultimately, some form of spigot. Electrical versions of these simple pumps are available where a motor replaces the traditional pump handle. This form of pump moves the water. But as anyone who has used an old-fashioned pump knows, it takes a lot of energy to move a little water.
Centrifugal Pump
- Similar in design to a fan, this pump has several blades, or impellers, that surround a central shaft. The pump will not start dry; water must fill the pump case entirely before the pump is switched on. This is called "priming the pump." Water is drawn into the pump through the inlet. The water is then rotated through the center of a round pump case by the impellers. Centrifugal force pushes the water outward, where it is forced through the outlet. The force of the outflow is dependent on how close the impellers are to the case of the pump. When there is a lot of space, the water slows down. Several centrifugal pumps can be used together to create higher powered outflow. When used together, they are called multistage centrifugal pumps.
Turbine Pumps
- Similar in design to the centrifugal pumps, turbine pumps stand vertically. In this case, the pump uses several smaller sets of impellers to draw water up the pump. Their thinner, vertical design makes them useful for underground water retrieval. But turbine pumps are more expensive and labor intensive than centrifugal pumps. Because turbine pumps must fight gravity, they need more power so their impeller blades are close to the casing. Silt, sand and other grits are constantly ground into both the blades and the casing of the pump. Its underground placement makes it difficult to inspect and maintain. Like the centrifugal pump, the turbine pump must be primed.

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