Self-Priming Pump: Frequently Asked Questions

What is a Self-Priming Pump?

A Self-Priming Pump is a pump capable of drawing liquid from a level lower than the inlet. They are used in installations where the pump is above the fluid being pumped, such as above a storage tank and depending on the make and model, can pull anything from sea level to 9m. It is also important that you are sure your application and installation require a self-priming pump because in some instances, these pumps can be less efficient than non-self-priming pumps.

What Self-Priming Pumps do Tapflo Pumps UK supply?

Some pumps require flood casing in order to achieve self-priming, whilst others can dry run and automatically self-prime. At Tapflo, we supply a large variety of pumps that are self-priming, which includes:

Diaphragm Pumps – Our AODD Pumps can self-prime suction 5m dry or 8m wet.  

Peristaltic Pumps – Tapflo UK are proud to work alongside Albin Pumps distributing their Peristaltic Pumps. These pumps can self-prime and have a suction of 9.8m dry or wet due to their operating principle.

Self-Priming Centrifugal Pumps – These pumps have 6m suction, but the head of the pump needs to be prefilled before use.

Tapflo supply our own Self-Priming Centrifugal Pumps that come in either Industrial or Hygienic options. Tapflo UK also distribute BBA Pumps’, Electrically Driven Self-Priming Centrifugal Pumps.

Twin Screw Pump – The Pomac Screw Pump, also available as a Double Screw Pump has a self-priming capability of up to 9 metres with water.

Flexible Impeller Pump – All of our Flexible Impeller Pumps (also known as Flexible Vane Pumps) are self-priming up to 6m dry.

What type of installation would Tapflo recommend a Self-Priming Pump for?

Before deciding whether you require a self-priming or non-self-priming pump, it is important to know whether your pump will be installed above the fluid or below it. If your pump will be installed below the fluid, the weight of the fluid will force your product into the pump, therefore you won’t require a self-priming pump. However, if your pump is going to be installed above the fluid, the pump will be pulling product out of the tank or storage container and it will be important to decide how much suction is required.

Your pump will be chosen based on the requirements of dry suction and wet suction, as the suctions often differ. For example, if the tank is 5.5m deep and the pump is installed above the tank, you could use a Self-Priming Centrifugal which has a suction of 6m, but if your tank was 9m deep, you would require a Peristaltic Pump or a Diaphragm Pump.

Therefore, we would recommend self-priming pumps for installations where the pump is required to be above the fluid.  

How does a Self-Priming Pump work?

As expected, not all self-priming pumps operate in the same way. Each type of pump has their own operating principle which is briefly explained below. For a more detailed explanation of how each pump works, head over to our product pages.

How does a Self-Priming Centrifugal Pump work?

Centrifugal Pumps draw in fluid from the suction port whilst pushing out all the air in the line and head out of the discharge. Once all the air has evacuated the system a vacuum will be created allowing the fluid to be sucked into the pump head.  Therefore, it is important for the pump to be filled before start-up to ensure the pump can operate correctly and efficiently.

Operating Principle of a Self-Priming Centrifugal Pump

What are the benefits of using a Self-Priming Centrifugal Pump?

  • - Suction Lift: 4.5m
  • - Ideal for highly aerated fluids
  • - Only the suction pipe needs to be immersed in the tank, meaning the pump will be easily accessible for maintenance
  • - Simple design
  • - ATEX rated
  • - Low maintenance costs
  • - Open impeller to handle solids

How does a Diaphragm Pump work?

Air Operated Diaphragm Pumps use compressed air to drive two diaphragms that work simultaneously to push liquid through the pump system. One Diaphragm creates a vacuum to draw fluid into the pump housing whilst the other diaphragm forces the fluid towards the discharge port.

How does a Diaphragm Pump work

What are the benefits of using a Diaphragm Pump?

  • - Can dry run without damage to the pump

  • - Self-priming up to 5m from a dry suction pipe and 8m from a wetted pipe.
  • - Simple design
  • - Few components for easy and fast maintenance
  • - Lubrication-free system
  • - Large range of Diaphragm Pump Accessories available for optimal control of your pump

How does a Peristaltic Pump work?

A roller in the centre of the pump presses on the walls of the rubber hose within the pump. The compression of the roller pushes the fluid forward inside the hose towards the discharge port while drawing fluid on the other side of the roller round and into the pump to start the process again.

How does a Peristaltic Pump work

What are the benefits of using a Peristaltic Pump?

  • - Only the hose comes into contact with the liquid being pumped, therefore, these pumps are seal-less

  • - Self-Priming up to 9.8m
  • - Continuous dry running with no damage to the pump
  • - Bearings are greased for life
  • - Easily maintained

How does a Twin Screw Pump work?

Tapflo supply a Double Screw Pump, this involves two screws within the pump rotating in opposing directions without touching each other. As the screws pass the suction port it creates a vacuum which draws liquid into the suction port of the pump housing.

What are the benefits of using a Twin Screw Pump?

  • - Self-Priming up to 8m

  • - EHEDG compliant

  • - Suitale for pumping fragile solids and shear sensitive fluids

  • - Discharge Pressure up to 16 Bar

  • - Can dry run

How does a Flexible Impeller work?

Flexible Impellers are a type of positive displacement pump that traps fluid between impeller vanes. As the impeller rotates, it forces the trapped liquid round, in a pulseless flow, and out through the outlet.

How does a Flexible Impeller work

Advantages of using a Self-Priming Pump

  1. 1. Self-Priming Pumps are ideal for completely emptying containers and tanks of fluid.
  2. 2. If the pipework or installation doesn’t allow for flooded suction, then you’re required to use a self-priming pump sat above the liquid.
  3. 3. Flexibility to change the instillation if required.

Why won't my Self-Priming Pump prime?

If facing this problem, the first things to check for are:

  • - Is the pump I’ve purchase a self-priming pump?
  • - Do I need to do anything to the pump before it starts running to make it self-priming? For example, some pumps need their chamber to be filled with fluid before start up, one pump that requires this is BBA’s B-Series Self-Priming Centrifugal Pump.
  • - Is there air in your suction line? Air in your suction line will preventing the pump from creating a vacuum to draw liquid into your pump.
  • - Has your pump been spec’d properly? For example, has the required pressure been calculated correctly, can your pump suck as far as it needs to?
  • - Is the pump sized correctly to overcome the suction and discharge pressure (total system pressure)?

Case Study

Tapflo have recently supplied a 2” Air Operated Double Diaphragm Pump to a large chemical factory, the pump was required to do the below application.

Flow: 300 LPM

Head Pressure: 4 bar

Liquid: Caustic Soda

Power Requirement:Pneumatic

Pipe Size:  2”


Tapflo jumped at the chance to supply this prestigious site with a solid block HDPE diaphragm pump as per the below spec.

Product code:T400 PTT

Connections:  2”

Max Flow:  440LPM

Materials:  HDPE Body / PTFE diaphragms, balls and seals.

If you’re interested in finding out more information about any of our Self-Priming Pump range, please get in touch with our team of pump experts.

Email: [email protected]

Call: 023 8025 2325

Alternatively, we’re available through the online chat in the bottom right hand corner of the screen.

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