Vaillant F24 Fault Code

Vaillant F24 is an error code that indicates that there is not enough water in the boiler.

You can cause it by something as simple and inadvertently coles isolation valves or a more serious problem like a faulty PCB.

This error affects the Turbomax plus 824/828E models, Ecomax Pro 18/28E, Ecomax Pro828E, Ecomax Pro 82E and EcoTEC 65kW models.

What does Vaillant F24 fault code refer to?

Although the Vaillant boiler F24 fault code focuses on one error, it can also be applied to multiple errors.

Your engineer will need to perform a diagnostic in order to determine the problem.

One of the following problems will be identified by the fault code:

  • Pump Failure
  • Closed isolation valves
  • Heating system or boiler?
  • Blockage of heat exchanger by debris

Is it easy to fix the F24 fault code?

The isolation valves beneath your boiler might have been turned off by someone who has just attended to it.

If they have, it will starve the heating system to get the water it requires to function.

Here is the end of the simple fix for F24.

An engineer will be able to diagnose the problem and inspect the parts to determine if the isolation valves are not the problem.

What does the Vaillant F24 Error signify?

Boilers work by allowing water flow through them and heating it at the same time. This requires constant water flow to function.

F24 errors indicate that the boiler is not working because there isn’t enough water in the system.

What Causes an F24 Vaillant Error?

F24 errors can be caused by a variety of reasons, which your engineer will be capable to diagnose.

Isolation Valves

The F24 could be triggered by the F24 if the boiler was recently serviced and the isolation valves have been left closed by accident. This is arguably one of the better options if this is why the Vaillant F24 fault occurs.

Faulty Pump

A faulty pump is one reason that can cause the F24 error code. This can happen in many ways as follows. A central heating pump can be replaced if this is what is causing the issue.

Internal components seized

The boiler could have suffered a failure or a seized component. It is easy to determine if this has occurred.

Your boiler pump should be warm but not too hot. A seized internal component can cause the motor to work harder and heat up.

If you feel the pump vibrating and it is very hot, then it’s likely that the problem is a seized part.


The Vaillant F24 fault can be triggered by debris caught in the pump.

The main heat exchanger can get clogged with water deposits, which heat sludge. This blocks heat flow and causes heat exchanger to become blocked.

The central heating system can also be affected by limescale or iron oxide buildups.

Speed Setting

There are a variety of speed settings for a boiler pump. Larger properties will need a faster setting, while smaller properties will require a slower one.

An F24 error is activated if the speed setting in a large property is too low.


An airlock is a small bubble of air that has been trapped within the system. It can significantly slow down or stop water flow.

The f24 could have been triggered by an airlock in your pump, or in a towel rail, radiator or other heating system.

Electrical Error

A malfunctioning pump or wiring problem could lead to a problem in communication between the PCB and the pump. This could trigger the F24 fault code on a Vaillant boiler

How to Fix an F24 Vaillant Error

If the error was due to closed isolation valves, the valves can be simply opened.

The problem with communication with the PCB will require you to replace it, which can cost around PS500. It’s not economically feasible to spend so much money fixing a boiler that is deteriorating. Instead, it is better to invest in a brand new boiler.

You can solve airlocks by squeezing the pump and any radiators or towel rails throughout your home.

An expert can inspect the affected components and give you advice on cleaning them or replacing them if there is debris.

Can you Fix a Vaillant F24 Error Yourself?

You can fix the problem by yourself if the isolation valves are broken. You will find the valves below the boiler. The slot for the screwhead will be parallel to the pipes.

If the valves are closed, the slots will be in a straight line with the pipes. This can be fixed by using a screwdriver.

A gentle tap on the pump side can sometimes free a stuck component. However, it is possible that the part is blocked with debris and needs to be addressed by a professional.

If you suspect the problem was caused due to an airlock, you can manually bleed it.

To stop water from entering, close the gate valves and release the bleed screw slowly. The air will make a hissing sound as it escapes and then be replaced with a drip of water once all the air is gone.

To restore water flow to your boiler, don’t forget about opening the gate valves at each end.

For good measure, you should also flush all radiators.


Is there a way to prevent the F24 error from happening?

This error could be due to water shortage. If you notice water pooling under your boiler, this could indicate a leak.

The central heating pump is the most likely source of a boiler leak. It could be a problem with the boiler’s new components, but the more likely reason is that the seals have worn.

Is there another type of circulation fault?

A blockage in your heating system can cause problems with circulation. This can be done with older heating systems with a hot flush or with newer systems with a pressure flush.

How can I stop the F24 error?

You can reduce the chance of F24 errors by installing a scale reducer to your heating system to prevent circulation faults. A magnetic system filter can be purchased that captures heating sludge.

Does the Vaillant F24 fault mean I need a new boiler?

All the top Gas Safe engineers are available to help you price your job. They could also advise if it may be time for a new boiler. Old boilers over 10 years old can really start to become less energy efficient as well as throw up more and more fault codes as time goes on. If the issue is your heat exchanger, then this is arguably one of the biggest problems and most costly repairs.

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