The Difference Between Diaphragm & Centrifugal Pumps?


Not sure whether to choose a centrifugal or diaphragm pump? Know the difference between centrifugal pumps and diaphragm pumps before you buy.

When you want to move liquid from one place to another, a portable water pump is a great piece of equipment for the job. But not all pumps are created equal. Some can transfer thicker liquids that contain solids... while some can't. So it's important to know how the different types of pump work and which one will be best suited to your task. Here, we look at two popular types of portable water pump: centrifugal pumps and diaphragm pumps.

Centrifugal Pump

The most popular hydraulic pump type in the world is the centrifugal pump.

The most popular engine for powering Petrol Water Transfer Pumps is Honda

How it works

The centrifugal pump is based on a simple yet effective method. When you turn the pump on, there's an increase in the liquid pressure from the pump inlet to the pump outlet. The pressure increase is created by transferring mechanical energy from the motor through the rotating impeller to the liquid.

The impeller is at the heart of the centrifugal pump. The liquid flows from the pump inlet to the impeller centre, and then out along its blades. When the impeller is made to rotate, the fluid surrounding it also rotates, which gives centrifugal force to the water particles.

The centrifugal force makes the liquid move radially outwards, and both the pressure and kinetic energy of the liquid increases. Meanwhile, at the suction side of the pump, water is being displaced. As a result, a negative pressure helps to suck a fresh liquid stream into the pump again, and the process continues.

Uses of centrifugal pumps

Trash Pumps are popular with tradesmen, farmers, builders, professional contractors and the hire industry

Because of their robust and simple design, centrifugal pumps are ideal for a wide range of water transfer applications. They are especially popular in building and trade, industry, petro-chemical, agricultural, food industry, marine applications and much more.

Types of portable centrifugal pumps include; water transfer pumps, trash pumps, , chemical pumps, submersible pumps, and fire fighting high pressure pumps:

Are you fire ready? Crommelins Fire Fighting Pump in Action

Diaphragm Pump

Diaphragm pumps are more suited to moving thicker liquids such as sewage and muck.

How it works

The most popular type of diaphragm pump works using compressed air as its power supply. There are two chambers, a diaphragm, an inlet check valve and an outlet check valve.

Air is driven into the bottom of an air cylinder, which raises the piston inside and lifts the diaphragm. As the diaphragm is raised, the inlet check valve ball is lifted and liquid flows into the pump. When the piston is at the top, the cavity is filled and the pump is ready to discharge the liquid.

Compressed air is forced to the top of the diaphragm chamber, pushing the diaphragm down and moving the liquid out of the pump cavity. The outlet check valve ball is then lifted, and the pump is ready to start again.

centrifugal pumps
Diaphragm Pumps are commonly used for Septic Tanks, Wet sandy substances, Effluent pits and the like.

Uses of diaphragm pumps

Portable Diaphragm Pumps are highly versatile and can be used in industrial, mining and general manufacturing plant service. Their design makes them ideal for pumping liquid that contains solids or has a high viscosity, as well as thin liquids. For example, they can be used to remove water from underground mines, sewage, and even some food transfer needs. They are also often used in effluent pits.

Air-operated diaphragm pumps are especially popular for when there's no mains electricity supply, or in areas with an explosive or flammable risk.

Another great feature of diaphragm pumps is that there are only three moving parts, so there's very little to repair or maintain.

Which pump should you buy?

Water Transfer Pumps; a great way to move water from once place to another around your property

Armed with the difference between portable centrifugal pumps and diaphragm pumps, there are two questions you need to answer:

  • Where are you using the pump?

  • What are you pumping e.g. liquid, liquid with some solids, etc.

Our overall recommendation is that for moving clear water, or water with small pieces of debris, then one of the Centrifugal Pumps is your best bet... however, if you are looking to move thick, viscous fluids, then a Diaphragm Pump is the go.

Whatever your water pumping requirement, just be sure to opt for a water pump that is powered by a quality engine such as Honda, Yamaha or Subaru and are backed by comprehensive warranties and national service agent support networks. It is not advised to buy a cheap, no name pump from the likes of eBay or discounted websites that do not offer national service agent and spare parts backing.

Now you can do your research into the best specific model pump for your application. Read our Buyer's Guide to Water Pumps or start by checking out our wide range of pumps!


DISCLAIMER* Please note, this advice is general in nature and we strongly recommend consulting the product manual and where relevant, a professional installer.

3 thoughts on The Difference Between Diaphragm & Centrifugal Pumps?

14 August 2020
In your article I learn both pump difference thanks, great information in your article and thanks for sharing such a good article this is very helpful.

31 January 2019
very informative article thank you for making us know the differences about diaphragm pumps

25 December 2018
Thank you for explaining the difference between the diaphragm pump and centrifugal pump. To know more about diaphragm and other air operated pumps visit

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