Vaillant boiler f22 fault

How to Fix Vaillant Boiler F22 Fault Code Repair

Last updated on June 10th, 2024

The Vaillant F22 fault code indicates low boiler pressure so it must be repressurised to fix it.

The first thing you need to do is check the pressure gauge and if it’s low, repressurise it until it’s at 1 to 1.5 bar.

I have been repairing boilers for over a decade and this is how I fix a Vaillant boiler F22 fault code most of the time.

Vaillant boiler pressure gauge

Vaillant Boiler F22

It could be other problems causing the F22 low water pressure fault code, but a leak is by far the most common reason for your boiler pressure dropping.

To fix this, you must repressurise the boiler, then it should start working again.

The F22 fault code should disappear when the boiler is repressurised, and you should hear the pump start to circulate the water in the boiler.

Vaillant F22 Fault Reset

The first thing I would check on a Vaillant boiler that is not working, no matter what fault code is showing, is to check the pressure and reset the boiler.

Knowing how to reset a Vaillant boiler is the simplest way to get your boiler working again, as it might have just locked out.

To reset a Vaillant boiler, you must find the reset button. This is usually a flame with a line through it.

You have to press the button to reset the boiler. Sometimes you have to hold it down for 3 seconds, but on some Vaillant boilers, it just needs to be pressed.

Vaillant Boiler F22 Error Keeps Happening

If your boiler is constantly losing pressure, showing F22 and going to lockout, then you most likely have a leak on the boiler or central heating system which needs to be fixed.

Or, if you have bled a radiator, then the pressure will drop and the boiler needs to be repressurised.

If the boiler pressure is dropping straight away after repressurising, then you must have a serious leak or an open-ended pipe on the central heating system.

This will need to be found and fixed to get your boiler working again.

Other Causes for Vaillant Boiler F22 Fault Code

Other causes for the Vaillant boiler F22 fault code, if it’s not low water pressure, could be:

  • Pressure sensor
  • PCB

How to Repressurise a Vaillant Boiler

To repressurise a Vaillant boiler, you must find the filling loop. If it’s a built-in filling loop, it will have two grey handles under the boiler.

Both handles must be turned to open and then closed when the pressure reaches 1 to 1.5 bar.

If it’s an external filling loop, it will probably be on two of the pipes under the boiler. It will most likely have two valves with black handles and a flexible hose connecting them together.

You must open both valves to repressurise the boiler, then close them both when it is repressurised.

You should be able to hear the water filling the central heating system when both valves are open, if not, then the filling loop might have problems or the house’s mains water might be turned off.

Vaillant Boiler Pressure Gauge

The main Vaillant boiler pressure gauge is a digital pressure gauge on the screen on the front of the boiler. You have to press multiple buttons to find and read it.

Vaillant boiler pressure gauge reading
Pressure gauge reading

Vaillant boiler have annoying manual pressure gauges which don’t have any numbers on them so most people don’t know if it’s on the correct pressure.

It always looks like the pressure is low, even though it’s not.

Vaillant Boiler Guides


The F22 Vaillant fault code is almost certainly caused by low boiler pressure.

You must repressurise your boiler to fix the problem and clear the fault code.

Feel free to ask me any questions in the comment section below and I’ll try my best to help.

Please share this post if you find it helpful.


Where is the pressure gauge on a Vaillant boiler?

The digital pressure gauge on a Vaillant boiler is on the screen on the front of the boiler, if it has one. You must press a button or two to access and read it.

There is also a manual pressure gauge which is usually under the boiler on the right-hand side. This is hard to read as there are no numbers on there.

Why does my Vaillant boiler keep losing pressure?

Your Vaillant boiler keeps losing pressure because you most likely have a leak on your central heating system, which could be at the boiler.

Another reason your Vaillant boiler keeps losing pressure could be an expansion vessel problem, or the pressure relief valves might be letting by.


  • Steven Reid

    I am a full-time plumber and Gas Safe registered engineer. I incorporated Housewarm Ltd. in 2011 to provide heating and plumbing services to homes in Newcastle upon Tyne, England. I now blog about what I've learned over the years to help DIYers and plumbers.

    View all posts
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