How Does a Water Pump Work?

Many people use the water that water pumps put out. You might be one of them, and that is why you probably want to know. Knowing how they work might help you understand what to watch for when there is a problem. Many houses have a well to draw out water from. A machine – a water pump – does this.

In order to know how a water pump works, you should first know what a water pump is. Let’s look at the details of water pumps.

What Is a Water Pump?

A water pump is an electrical device that draws out the water that is already in the ground. They speed up the rate at which the water flows out. When the flow of the water speeds up in the pump, low pressure builds up at the intake. This creates a vacuum. As the water comes out of the low-pressure end, high pressure is created in the inlet. This pushes the water to come out with force.

Understanding how a water pump works is not that simple. There are many types of water pumps. The working principle of the water pump changes as the type changes. In this article, we will discuss three different types of water pumps.

Centrifugal Water Pump

This water pump works by using a device called the impeller. This device has blades that direct the water flow through the pump. Centrifugal water pumps come in different designs such as submersible, trash, and standard. These pumps are known to work well with thin liquids. They provide good flow.

Working Principle

The impeller lies right at the heart of the pump. It has a number of curved blades. You can fit these blades with shroud blades. There are various designs of impellers as well such as open, closed, and semi-open. Centrifugal water pumps are very efficient. The impeller in these pumps is always submerged in the water. That is how it can work its magic.

When you switch the pump on, the blades on the impeller rotate; in return, the liquid around it rotates as well. Because of the rotation, it produces a centrifugal force, which causes the water to radially move out. That is why these pumps are named centrifugal.

When the rotational energy is imparted to the water particles, both the kinetic energy and pressure of the water will increase at the discharge ends of the impeller. At the part of the water pump where suction occurs, water gets displaced. This induces low pressure in there. The water is drawn into the system thanks to this low pressure.

This is where a cyclic process starts. In centrifugal pumps, the impeller is placed inside a casing. The casing traps the water moving inside it and allows it to rotate in the same direction of the impeller and then to the water outlet. The casing increases the area of the impeller, which helps it accommodate the coming flow of water. This also helps in the creation of static pressure, which is essential for overcoming the water pump resistance.

Common Problem

One common problem with centrifugal water pumps is that they encounter air a lot. When the air gets trapped in them, they become air-bound. This means that they will lose the ability to pump out water efficiently.

Self-Priming Water Pump

These water pumps solve the problem you face with centrifugal pumps. They prevent air from building up in the pump. The purpose of these pumps is to mix water with air. A fluid is then made that can be easily pumped out. The rest of the process is the same as the centrifugal pump. This pump just gets rid of the moving air.

Working Principle

Unlike centrifugal water pumps, these pumps have a reservoir built into the unit. The air is removed inside the pump by recirculating the water in the priming process. The water reservoir is usually constructed above the impeller or in front of it. In these pumps, the water needs to be there in the reservoir. It is advisable to never run these pumps without water. Otherwise, you may damage the pump. It could also be dangerous.

Common Problem

These problems are very easy to operate but still, people commonly encounter some issues with these pumps. One such problem is noisy operation. The reason for that could be either mechanical or hydraulic. We recommend you call an expert in this case.

Positive Displacement Water Pump

These pumps are kind of similar to centrifugal pumps, but the difference is that they use mechanical energy to draw water out. They have two designs normally. They can either be rotary pumps or reciprocating water pumps.

Working Principle

There are single-acting and double-acting reciprocating positive displacement water pumps. If the displacement is only on the forward stroke, then the pump is single-acting. If it displaces water both on forward and return strokes, then it is double-acting. A reciprocating water pump is double-acting. These pumps are capable of delivering high pressures. In case the pressure gets very high, there is a relief ale in place to protect the pump.

Many positive displacement pumps are of rotary types. They rotate constantly and displace water with every revolution of the pump shaft. The water moves in slowly and moves out of the pump with force. There is a clearance in the pump, which separates the suction from discharge. These pumps are self-primed.

Common Problem

There are many common problems that you could encounter with these pumps. One of them is when there is no water flow. It usually occurs when the pump is not primed. It could also happen if the pumping unit is worn out.


There are quite a lot of types of water pumps. All of them work in almost the same way. But as you may have noticed, you can solve the problem of one pump with another. This article just gives a general overview of the working principle of some water pumps. They are all very efficient at increasing water pressure.

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