Vaillant Boiler F22 Fault Code Explained and How to Fix It

The underlying issue behind the Vaillant boiler F22 fault code has to do with low water pressure. The fix for the F22 error doesn’t need to be expensive or complicated, however, on occasion, the boiler will need to be dismantled, and you’ll need help from a Gas Safe engineer.

The F22 fault code is one of the most common error codes on Vaillant EcoTEC boilers. Below, we’ll explain exactly what F22 means, and outline the most cost-effective way to fix it.

Vaillant Boiler F22 - Error Code

What Does Vaillant F22 Fault Code Mean?

The Vaillant boiler F22 error code indicates low water pressure. This may be caused by insufficient water in your heating system or a system that leaks (the boiler pressure is consistently dropping in the latter scenario).

Understanding Fault Codes

The Vaillant F22 error isn’t as serious as many others — typically, a heating engineer can easily find and fix the problem.

Note that your boiler will stop working before showing the error code; this is a precautionary measure that ensures the boiler isn’t operating in conditions that could cause damage.

A drop in pressure could mean your system is running dry, which will overburden (and prematurely wear out) expensive components, like the pump and heat exchanger.

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How to Fix F22 on a Vaillant Boiler?

Before we go any further, note that you’ll need to call a Gas Safe engineer, as the fix may require the boiler to be taken apart.

Check the Water Pressure Sensor

The first step is to check if your Vaillant boiler has low pressure. Ideally, you want to see it at approximately 1.5 bar. If it’s hovering around the 1.5 bar mark, yet the boiler is locking out and displaying the F22 fault, your boiler engineer will want to see if the water pressure sensor is working properly.

A faulty sensor may be sending signals to the printed circuit board (PCB) that the pressure is lower than it is, triggering the lockout sequence when it shouldn’t. In this case, the fix will involve replacing the sensor.

Monitor Boiler Pressure

If your boiler’s pressure has dropped below 0.5 bar, the lockout is legit — your boiler doesn’t have enough water (or pressure) to operate smoothly.

You’ll notice your boiler pressure dropping if there are leaks. The leak might not be visible, but consistent pressure drops usually indicate a leak in the system.

Inspect the Heating System For Leaks

To increase pressure, you need to add water to the system. But before doing this, you’ll want to check that your boiler, and any parts in the central heating system, aren’t leaking. If they are, the leaks could damage components inside the boiler, or even ruin plasterboards and flooring (assuming it’s a leaking copper joint).

Get a Gas Safe engineer to check the following for leaks:

  • The boiler (in particular, the pump and heat exchanger)
  • Radiator valves
  • Joints in copper pipework

If there are leaks, your heating engineer will fix them BEFORE topping up your boiler with water.

Top Up Your Boiler’s Pressure

The next step is to top up your boiler’s pressure. With modern boilers, this is easy. Usually, you’ll find a small braided hose just underneath the boiler — this is the external filling loop. Opening this valve will allow water into the system. Simply close the valve when you’ve hit the desired reading on the pressure gauge.

Typically, we’d expect a boiler’s pressure to be set at around 1.5 bar, but always check your manufacturer’s handbook to ensure it’s not more or less.

Reset Your Boiler

With the sensor checked, leaks sealed, and the boiler’s pressure topped up, now it’s time to reset your boiler.

As the boiler resets, the PCB will check the readings from the water pressure switch, and, assuming it’s been topped up to the correct pressure, your boiler will fire up right away.

Other Vaillant Boiler Problems

If the F22 boiler fault code hasn’t been cleared using the process outlined above, there might be other problems with your Vaillant boiler. On some occasions, multiple errors occur at once, which only adds to the confusion.

So, jump over to our guide that covers the most common Vaillant fault codes and boiler problems here.

Failing that, we’ve also curated some of our pages covering various boiler errors in our boiler fault finding guide here.

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Hopefully, our post has cleared the Vaillant F22 fault code from your boiler. If you’re still stuck, email us via the contact form below, and we’ll do our best to help you out as soon as possible.

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