Vaillant F22 Fault Code Explained and How to Fix It

If your Vaillant boiler is showing an F22 fault code and you are at a loss to work out what’s wrong, this is the guide for you. In this short guide, we will tell you what this error code means, what the likely cause is, and also explain how you can fix it.

Vaillant boilers are pretty reliable but even they go wrong from time to time. More often than not it is the same faults that we see cropping up again and again and the F22 error code is perhaps the most common, especially on their EcoTEC models.

The good news is that, in general, this isn’t an expensive or complicated issue to fix. However, there are some scenarios that might require the boiler to be dismantled and you will need an engineer to do this for you.

Otherwise, this is an issue you can usually fix yourself and in this guide, we will show you how.


What Is The F22 Fault Code?

The F22 error code on Vaillant boilers is an issue to do with low water pressure.

It will usually be caused by insufficient water in your heating system and this will more often than not stem from a leak. Leaks will cause the drop in boiler pressure and this will, in turn, trigger an F22 error code when the pressure drops too low.

An F22 error code is something that needs addressing but it is something that can usually be fixed quite easily. But it is important to address the problem as soon as possible because low water pressure can cause key components in your boiler to overwork and if they do this for too long, they can wear out and leave you with an expensive repair bill.

A Step-by-Step Guide to Fixing An F22 Error

#1 – Check Your Boiler’s Water Pressure Sensor

The first thing you need to do if you get an F22 error on your Vaillant boiler is to check your boiler’s water pressure sensor.

The pressure in your Vaillant boiler should usually be around 1.5 bar. If it is around this but the F22 error is showing, the issue is likely to be with the sensor itself.

In this case, you will need to get an engineer to take a look and you might need to get a replacement sensor.

#2 – Monitor Your Boiler’s Pressure

If the pressure in your Vaillant boiler has dropped to below 0.5 bar, this will be the reason that you have locked out. It means there is not sufficient pressure for your boiler to operate safely and it is likely to cause more serious damage if it tries to do so.

If the pressure has dropped this far, it is likely that a leak is causing the problem. The leak may or may not be visible but the pressure drop is the tell-tale sign.

#3 – Check For Leaks

If you suspect there is a leak, you can check your own system for evidence.

Take a look at the boiler itself and the pipework that feeds it. Then look round all your radiators and towel rails as well as any exposed pipework to see if there is any evidence of water leakage. It might not be a big leak. Even a small leak can cause significant pressure loss over time.

Some leaks are caused by loose joints or incorrectly fitted pipework. If this is the case, you should be able to fix this just by tightening the relevant joint.

If you cannot find evidence or a leak or it is in a place you cannot fix yourself, you will need to get a qualified engineer out to take a look at the boiler itself, your radiator valves, and the pipework in your central heating system.

#4 Top Up Your Boiler’s Pressure

Once the leak has been fixed, the next step is to top up your boiler’s pressure, If you have had to call an engineer they will do this for you, but it is something you can do yourself too.

On most modern boilers, you will find a small braided hose just underneath the boiler. This is called the external filling loop and can be used to increase pressure in your system by adding water.

Open this valve and the pressure in your system should increase. When it has reached the right pressure, simply close the valve again.

You will want to set the pressure in your Vaillant boiler at around 1.5 bar usually, but always check your boiler manual to make sure this is correct for your model.

#5 – Reset Your Boiler

Once you have topped up the pressure in your Vaillant boiler, you will then need to reset it. This is usually done using the reset button.

Most Vaillant boilers will have this situated next to the display panel but this can vary depending on your model. If you can’t find it, check your manual again.

Hold down the reset button for the required amount of time. This will trigger the reset sequence which might take a few minutes to complete. When it is complete, your boiler should function again as normal.

Other Possible Problems

If you have followed this process, either on your own or with the help of an engineer, and the F22 fault code is still showing, it is possible that the cause of the error message could be a different issue.

Sometimes boilers can succumb to multiple errors at the same time and this can lead to confusing error codes being shown.

If you think this might be the case with your boiler, take a look at our guide to the most common Vaillant boiler problems here. This details all the most common issues that can occur with Vaillant boilers and explains how to fix them.


The Vaillant F22 is a common issue which lots of their customers have reported. Usually, it is a simple issue to fix, but sometimes you might need the help of a qualified engineer.

In this short guide, we have explained the likely reasons for an F22 error code and how to deal with it. Sometimes you will be able to handle the issue yourself, but there will be times when you need an engineers’ help.

Have you had an F22 error code showing on your Vaillant boiler? How did you resolve it? Do you have any questions we haven’t answered in this guide?

We always try to respond to all comments and questions posted on our site, so please feel free to leave yours in the comment box below.

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