Last updated: August 7, 2021

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Centrifugal pumps are used in many different areas. On the one hand, they are used in private areas and on the other hand in economic areas. They help you to transport a fluid from one container or place to another.

With our large centrifugal pump test 2021 we would like to offer you some help in choosing a suitable centrifugal pump. Whether you need a radial, axial or diagonal centrifugal pump depends almost exclusively on your application. In the following, we have compared several centrifugal pumps for you and highlighted the respective advantages and disadvantages.




The most important facts

  • The centrifugal pump, which belongs to the type of fluid flow machines, is a technical machine for moving a fluid from point A to point B.
  • Centrifugal pumps are used in building services, water supply and waste water supply. They are also used for rainwater harvesting systems, toilet flushing and much more.
  • Centrifugal pumps are used in both commercial and private applications. The area of application is decisive for the choice of a specific model.

The best centrifugal pump: Our picks

Buying and evaluation criteria for centrifugal pumps

In the following section, we will show you which purchase and evaluation criteria you can use to make a decision on a model.

The following criteria are decisive for your purchase decision:

The purchase and evaluation criteria are explained in detail below.

Fluid

Centrifugal pumps are used in building services engineering as well as in water supply and sewage disposal. For example, you can use them for rainwater harvesting systems, toilet flushing and irrigation systems as well as in fountains or aquariums.

It should be taken into account here that different pumped media also have different viscosities. Viscosity describes the density as a function of temperature and pressure.

A centrifugal pump generates the highest pressure at a flow rate of zero. This occurs when the outlet (slide valve) is closed.

It is particularly important to remember that standard centrifugal pumps must be filled with fluid before they are put into operation. Furthermore, no more air than the critical quantity should enter the suction line during use.

In case of entry, the delivery would collapse. In the meantime, however, there are special models. These can vent the suction line automatically when they are filled.

Capacity / delivery volume

The flow rates of centrifugal pumps can range from 1x10-5 to 60 m³/second. The resulting delivery heads vary depending on the design and can reach a value of up to 5,000 metres.

The design and the area of application are decisive for the adaptation of the speed. This can range from less than 1,000 to 30,000 revolutions per minute.

Design

Centrifugal pumps are widely used because of their simple and resilient design. However, the design of the centrifugal pump is a decisive criterion for the application possibilities. However, it must be taken into account that there are different designs for each pump component.

The different combination possibilities result in a variety of centrifugal pumps.

So let us come to the two most relevant distinctions. The terms radial and axial are often used in connection with centrifugal pumps. They indicate the direction of flow at the outlet of the impeller.

With the radial pump, as the name suggests, the fluid exits the impeller perpendicular to the pump shaft. The opposite of this is the axial pump. With this pump, the fluid is conveyed parallel to the pump shaft.

Self-priming capability

The self-priming capability means that the centrifugal pump is able to convey fluids with a special system. However, this does not mean that the pump only needs to be connected and then performs. Caution The term self-priming is a little misleading here.

Before commissioning, the centrifugal pump must be filled with the medium via the intended inlet. To prevent backflow of water, a non-return valve is recommended as a connection to the suction hose.

This way you do not have to fill the pump with water again before the next start-up. The centrifugal pump can be emptied again via the drain provided.

Centrifugal pumps: Frequently asked questions and answers

In the following section we will give you answers to frequently asked questions:

What is a centrifugal pump?

A centrifugal pump is a pump that belongs to the class of fluid flow machines. It works through a rotary motion and dynamic forces and is mainly used to pump liquids.

An electric motor drives the pump shaft. The fluid to be conveyed enters the centrifugal pump via the suction pipe. Here, the medium is captured by the rotating pump impeller and then carried to the outside.

Kreiselpumpe

The use of a centrifugal pump can increase the water pressure in the garden or house. (Image source: Oleg Magni / Pexels)

The impeller, which rotates in the liquid, generates a pressure that rises towards the outside. Depending on the shape and design, the fluid is moved parallel (axially), vertically (radially) or diagonally.

This phenomenon can be easily simulated with a bowl of dough and a whisk. The bowl takes on the function of the centrifugal pump and the dough the function of the fluid to be conveyed. The whisk is the impeller that creates the flow.

The rotation of the whisk ensures that the dough lowers in the middle of the bowl. At the same time, however, the level at the edge of the bowl rises. The force acting there is also called centrifugal force.

Now imagine that there is a hole in the outer wall of the bowl. The dough would then flow through the hole and be transported.

Who is a centrifugal pump suitable for?

Centrifugal pumps are used in many areas of the economy as well as in the private sector.

In this sense, they are suitable for everyone. The decisive factor is what exactly a centrifugal pump is to be used for. The multitude of different models are used in a wide range of applications. Consequently, it is not possible to determine for whom a centrifugal pump is suitable.

The decisive question when buying a centrifugal pump is rather for which application it is to be used. In general, it can be said that the operability of the pumps is simple and quick to understand.

This also applies to larger and more complex machines that are used in industry, for example.

Centrifugal pumps are ideal for increasing water pressure. (Image source: analogicus / pixabay)

However, it is important that you consult the manual before using the pump. This will give you a brief overview before you start using the pump, and you can then operate it properly.

It is also important to consider the area in which the centrifugal pump is to be used.

Accordingly, a model should be selected that is up to the requirements. Differentiation criteria that should be taken into account include the type of construction and the type of energy conversion.

Furthermore, centrifugal pumps can also be used in the wastewater sector, in chemical process engineering, in petroleum processing and in the food or pharmaceutical sector.

What types of centrifugal pumps are there?

The following table lists the different types of centrifugal pumps and explains the relevant advantages and disadvantages.

Type advantages disadvantages
Axial pumps suitable for high pressure, infinitely variable pressure adjustment from 0 bar to maximum pressure, insensitive to dirt, easy to start up, insensitive to temperature expensive to purchase, complex design, high maintenance and monitoring requirements, increased risk of cavity formation, high energy requirements
Radial pumps also suitable for viscous materials, wide range of applications, low susceptibility to faults, low installation and repair costs large space requirement, most precise alignment of pump and drive required
Centrifugal immersion pumps for heavily contaminated media, for pumping viscous fluids at a temperature of up to 95 degrees Celsius contains a microswitch that can break quickly, it must not run dry for long (max. 30 seconds)
self-priming centrifugal pumps can vent themselves automatically, do not need to be filled with liquid before use they consume more energy than a normal-priming pump

An axial-flow pump delivers the fluid with a rotary motion parallel to the pump shaft. The resulting pressure difference in the pump is the driving force for the volume delivery. The radial pump has the largest number of different model variations. In this model, the fluid is conveyed perpendicular to the pump shaft.

A submersible centrifugal pump, on the other hand, is ideal for circulating aggressive fluids. They are particularly well suited for large flow rates. The opposite of the submersible centrifugal pump operated in water is the self-priming centrifugal pump.

This pump model is used exclusively outside the medium to be pumped. Insofar as the pump does not have a dry protection function, the fluid must be filled in via an inlet up to a specified mark before use.

What does a centrifugal pump cost?

When choosing a centrifugal pump, price also plays an important role. There are many different models of centrifugal pumps. Accordingly, you should also look at the different price segments before making a purchase decision.

A price comparison as well as a model comparison are indispensable in this area. Comparing models of centrifugal pumps in particular is not that easy. First of all, you should define the area of application precisely in order to be able to compare the different price classes.

Depending on the area of application, the costs are either high or low. Of course, this is always in the eye of the beholder. In this context, however, it should be mentioned that the average cost of a normal, simple pump is 50 euros upwards.

However, there are no limits to the price segment for centrifugal pumps. Whether a multistage or propeller-type centrifugal pump is to be purchased is of course decisive for the price determination.

Type price range in euros (€)
Centrifugal pump self-priming approx. 90.00 - 200.00€
Centrifugal pump with petrol engine approx. 150.00 - 400.00€

It should also be mentioned that a centrifugal pump with a lower capacity is usually cheaper than one with a high capacity. However, the price is also influenced by the brand, the quality standards and the materials used.

If you want to use the centrifugal pump as a domestic water system or in the garden, a 12-volt centrifugal pump is usually perfectly adequate.

Kreiselpumpe

To choose a suitable centrifugal pump, you should preferably consult an expert. (Image source: Pashminu Mansukhani / pixabay)

Of course, centrifugal pumps are also available on the internet. For example, Amazon or Ebay offer such products. It is advisable to read the reviews of the product carefully in advance.

There are also industry-specific suppliers who offer their centrifugal pumps on their websites on the internet.

What alternatives are there to a centrifugal pump?

The following table lists pumps that are suitable as alternatives to centrifugal pumps, including a brief description:

Alternative Description
Piston pump Piston pumps are used to pump liquids and gases. They can achieve very high pressures and the volume to be pumped can be determined with dimensional accuracy.
Jet pump A jet pump is based on the principle of generating a so-called fluid jet. It can be used for both motive and suction media.
Diaphragm pump Diaphragm pumps are well suited for both liquids and gases. On the one hand, they are suitable for continuous use and, on the other hand, they are insensitive to contamination. They are preferably used in areas where leak-free pump designs are indispensable.
Domestic waterworks A domestic waterworks is also a pump that transports water from an extraction point to a consumption point. They can be used in a wide range of applications and ensure continuous pressure in the water pipe.

It should be noted that centrifugal pumps are used more frequently than other pump models. This is due to the fact that they come in many different models and variations. In addition, the different models are often available in different performance classes.

However, if you need a metering pump, the piston pump would probably be the better choice. Another recommendable alternative is the jet pump. It is preferred when a fluid jet is to be generated.

Furthermore, the jet pump is particularly suitable for making water from a rain barrel or a container technically usable.

Diaphragm pumps, on the other hand, are preferably used to pump off sludge. Finally, we would like to introduce the domestic waterworks.

The term domestic waterworks is also generally known as a booster pump. With its help, as the name suggests, the water pressure in the water pipe can be increased.

How is a centrifugal pump started up?

When starting a centrifugal pump, you should first take a look at the enclosed manual. The manual is usually very detailed and provides a lot of information about the start-up.

With centrifugal pumps, start-up refers to the process of switching on. In other words, it means the process until the pump reaches the desired operating state.

Here you should choose the procedure that is gentlest for the material. This ensures that the centrifugal pump is not damaged. Depending on the type of pump, specific procedures must be carried out differently.

For example, so-called submersible pumps, which are used to transport fluids from containers or tanks, must be inserted into the medium beforehand.

Furthermore, it must also be taken into account that centrifugal pumps must not run dry, otherwise they will break down. You should therefore find out in advance how the pump must be filled with the fluid before it is put into operation. The manufacturer has specific fittings that should be used for this purpose.

When starting up, the variables torque, shaft coupling and speed must be taken into account. At the same time, the power is a variable that must also be taken into account. Furthermore, the non-return valve should not be disregarded.

What is a characteristic curve for centrifugal pumps?

A characteristic curve refers to a functional curve between two physical quantities. They are characteristic for a component or a device.

The characteristic curve of a centrifugal pump visualises the course of the flow rate in a diagram. Relationships between pressure increase and flow rate are shown graphically.

The impeller, the pump casing and the specific speed influence the characteristic shape of the curve. However, the viscosity of the pumped fluid is not taken into account in the characteristic curve.

In addition, an expert can read from the characteristic curve whether a centrifugal pump is running fast or slow. Furthermore, the technical requirements can be assessed, which are highly relevant for the installation. When the centrifugal pump works against a closed gate valve, the highest pressure is generated.

This process is described as zero delivery. The delivery pressure can be increased by connecting several pumps in series. Consequently, the delivery pressure adds up when they are switched simultaneously.

Conclusion

A centrifugal pump is a technical machine. It is used to transport a fluid from point A to point B. Centrifugal pumps are used in many different private and commercial areas. There are corresponding centrifugal pump models for the different applications.

Basically, it can be said that centrifugal pumps are very durable and resilient. This is due, among other things, to their robust construction. They are therefore often used in the garden for irrigation.

Image source: Popov / 123rf

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