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The Vaillant F22 Fault Code Explained [And How To Fix It]

One of the most common error codes on Vaillant EcoTEC boilers, is the F22 fault code.

In general, this isn’t an expensive or complicated fix. However, on some occasions the boiler will need to be dismantled. And, that’s going to mean that you’ll need help from a Gas Safe engineer.

Below, we’ll explain exactly what the F22 fault code means, and the most cost effective way to fix it.

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The Vaillant F22 Fault Code – Explained

The F22 error code on Vaillant boilers relates to low water pressure. This will be caused by insufficient water in your heating system, or a leaking system, meaning that boiler pressure is consistently dropping.

Understanding Fault Codes

The F22 error, isn’t as serious as many others. The problem can be easily found and fixed by a heating engineer.

Your boiler will have stopped working before showing the fault code. This is a precautionary measure to ensure the boiler isn’t operating in conditions that could cause damage.

A drop in pressure could mean your system is losing water, running dry, and that’s going to overwork (and prematurely wear out) expensive components like the pump and heat exchanger.

How To Fix It – Step By Step

Before we go any further, it’s worth noting that a Gas Safe engineer will need to be called, as the fix may require the boiler to be taken apart.

  1. Check The Water Pressure Sensor

The first step is to check your boiler’s pressure is correct. Ideally, you want to see it at around 1.5 bar. If it is around 1.5 bar, yet the boiler is locking out and displaying the F22 fault code, your boiler engineer will want to focus their attention on the water pressure sensor.

It’s likely to be sending signals to the printed circuited board (PCB) that the pressure is lower than it is, causing the lockout sequence to be triggered, even when it shouldn’t be. Typically, the fix will involve replacing the water pressure sensor.

  1. 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.

When leaks are present, you’ll notice your boiler pressure dropping. It might not be visible, but over hours or days, if you’re seeing pressure dropping on the pressure gauge, this indicates there is a leak in the system.

  1. Inspect The Heating System For Leaks

To increase pressure, you need to increase the amount of water in 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, they could cause damage to components inside the boiler or even damage 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 be able to fix them BEFORE topping up your boiler with water.

  1. 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, that’s the external filling loop. Opening this valve will allow water into the system. Simply close the valve when you’ve hit the desired pressure on the pressure gauge.

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

  1. 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 sensor/switch, and, assuming it’s been topped up to the correct pressure, it’s going to fire up right away.

Other Boiler Problems

If the F22 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 boiler problems here.

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

What’s Next?

Hopefully that’s cleared the Vaillant F22 fault code from your boiler.

Still stuck? Email us via the contact form above, and we’ll do our best to help you out as soon as possible.

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