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Vaillant Boiler F22 Fault Code


The Vaillant fault code F22 on the boiler is a common error on boilers and here we will explain in great details from questions asked to answers given. Please visit our emergency boiler repair page if you would like to use our service.


The Vaillant Boiler Fault Code F22 Fault Code Common Q&A


Just below, we have a list of common questions relationing to the F22 fault code on the Vaillant boiler.

Vaillant Boiler F22 Fault Code Error
  • What does the Vaillant Boiler F22 fault code mean?
  • Does a F22 fault appearing mean I need a new boiler?
  • Should I switch off the mains water if I have a F22 fault appearing?
  • How much will it cost to fix the F22 fault?
  • What’s the quickest, easiest and cheapest way to fix a F22 boiler fault?
  • How do I find the filling loop on my Vaillant boiler?
  • How much pressure does my Vaillant boiler need?
  • What’s the easiest way to find the leak causing the F22 fault?
  • If my boiler is leaking, causing the F22 error, is it dangerous?
  • I can’t find any leaks, what else can cause a F22 error?
  • There’s a pipe dripping on my Vaillant boiler, is that causing the F22 fault?

What does the Vaillant Boiler F22 fault code mean?


Boilers only work correctly when the system is within operating pressure.

Every Vaillant boiler is fitted with a pressure sensor, which detects when pressure is too low, or too high.

When pressure drops below 0.6 bar on Vaillant boilers, you’ll notice a flashing light on the display.

Once this gets to a critical stage (below 0.3 bar, according to Vaillant) the boiler will lockout and display a F22 fault code.

The central heating system now doesn’t have enough pressure for the boiler to operate correctly.

What do Vaillant recommend I do about the F22 error?


Vaillant state that the boiler will not operate correctly, without the heating system being filled with additional water. In turn, this will increase the pressure.

Please bear in mind, this is not a “fix”.

Pressure loss is due to a fault in the system. And, without running a diagnostic, it’s hard to pinpoint exactly what it is.

The most common cause of a F22 fault and a boiler losing pressure, is a simple leak.

This could be from a faulty radiator valve, a pin-hole in a radiator or pipe work, or a leaking soldered joint on an old copper fitting.

Does a F22 fault appearing mean I need a new boilerg?


99% of the time; no. The leak is the problem, not the boiler.

The boiler is simply doing its job, by locking out and displaying the F22 fault, so that the boiler doesn’t work at a pressure, that could damage expensive internal parts.

Should I switch off the mains water if I have a F22 fault appearing?


If you want to be safe; yes. Most leaks are minor, but the location of the leak is what can cause problems.

For example, a leak could be a weak soldered joint that’s behind a plastered partition wall. Even the smallest of leaks could ruin the plaster, and re-plastering is an additional expense you don’t want.

That said, most leaks that cause a F22 fault are little more than a drip.

Jump over to the pressure gauge (located on the front of the boiler).

If you can visually see the needle (and therefore, pressure) dropping, there’s a good chance the leak is more than just a drip, and it’s worth switching off the water at the mains.

How much will it cost to fix the F22 fault?


This depends on the individual fault. A simple leak due to a faulty radiator valve could be fixed in 1-2 hours, costing around £80-100.

On the flip side, a leak that’s caused a pump failure could cost in the region of £250-300, including parts and labour.

What’s the quickest, easiest and cheapest way to fix a F22 boiler fault?


Get a heating engineer to locate the leak (for example, a weak joint) and fix it (replace the fitting and re-solder the joint).

Once the leak has been located and fixed, the boiler will need to be re-pressurised.

You’ll do this by opening the filling loop on the boiler.

What’s the quickest, easiest and cheapest way to fix a F22 boiler fault?


Most modern Vaillant boilers will have a filling loop that is easy to locate, under the boiler casing.

Open the filling loop to add water and to increase the pressure.

Close the valve once the pressure reaches the optimum level.

How do I find the filling loop on my Vaillant boiler?


Most modern boilers will work at their best, when the system is set to 1.3 bar. Some engineers will suggest 1.5 bar, and that’s because it’s easier to remember.

In terms of fixing the F22 fault code on your Vaillant boiler, you’ll need to get pressure above 0.6 bar.

So, setting the pressure to the optimum of 1.3 bar will be more than enough.

How much pressure does my Vaillant boiler need?


Most modern boilers will work at their best, when the system is set to 1.3 bar. Some engineers will suggest 1.5 bar, and that’s because it’s easier to remember.

In terms of fixing the F22 fault code on your Vaillant boiler, you’ll need to get pressure above 0.6 bar.

So, setting the pressure to the optimum of 1.3 bar will be more than enough.

What’s the easiest way to find the leak causing the F22 fault?


Central heating system leaks are a pure fault-finding mission.

They’re not like modern cars, where you can plug a computer in and it tells you the problem.

Luckily, 99% of leaks are visible. Start with the most visible, and the most obvious:

  • Are any joints to copper pipes leaking?
  • Can you feel moisture around radiator valves, or where they connect to radiators and towel rails?
  • Are the connections to the boiler leaking?
  • ï Can you see any wet patches where pipes enter the wall?

If you’ve managed to locate a damp patch, you’ll want to wipe it down with blue roll. Once it’s bone dry, dab the area you think is causing the issue.

Remember, just because moisture has found its way to a fitting, doesn’t mean that’s the issue.

A typical example might be a pin-hole in the back of a towel rail.

The water will drip down to the towel rail valve, potentially making it look like the valve is leaking, not the towel rail itself.

Other parts in the central heating system could also be the issue. They include parts such as the PRV (pressure release valve), the boiler pump, auto air vent or expansion vessel.

Problems with those components deserve their own explanation, and will require a qualified engineer to fix the problem.

If my boiler is leaking, causing the F22 error, is it dangerous


Boilers go through rigorous safety testing, and that includes safety testing regarding leaks and electrical components.

Most electronics within the boiler are sealed units. They are designed to short (or the boiler to lockout) if they meet water.

Does that mean it’s safe? Not necessarily. Never take unnecessary risks.

If you see water dripping from your boiler, switch it off. And, not just for your own safety.

If water does manage to find its way into components like the PCB (printed-circuit-board, the electronic heart of your boiler), it’s possible that it will cause additional, expensive faults.

Why would my boiler be leaking?


There are a lot of reasons your boiler could be leaking. But, there’s one problem that comes up more than most; boiler pump faults, especially with older boilers.

Many older boilers were fitted with Wilo pumps.

Manufacturers quickly realised that Wilo pumps weren’t as reliable as they thought.

And nowadays, most manufacturers (even budget ones like Glow-Worm), use higher quality pumps such as Grundfos.

A common reason your boiler pump is going to be leaking, will be due to failed pump seals. They’ll either have deteriorated over time, or they’ll have been exposed to a pressure that’s too high.

Pumps have speed/flow settings (Grundfos UPS2 pumps have 1, 2, and 3, with 3 being the fastest).

And, some properties will get away with using a low setting (1). Using a high (3), could result in back-pressure that blows the pump seals.

I can’t find any leaks, what else can cause a F22 error?


The pressure gauge on your Vaillant boiler could be the culprit, but it’s unlikely. If there’s one component that’s likely to outlive a boiler, it’s the pressure gauge.

I’d never suggest running a test on a pressure gauge without contacting an engineer.

An obvious test would be to fill the system up with water. If the gauge doesn’t move, that could be a sign of a pressure gauge fault.

But, what else could it be a sign of? A lot of water escaping elsewhere on your system, and potentially causing damage to your property!

There’s a pipe dripping on my Vaillant boiler, is that causing the F22 fault?


It’s likely you are referring to the condensate pipe.

The condensate pipe looks like this:

Like vehicles that use fuel, boilers also create waste gases.

And, like an exhaust on a vehicle, the condensate pipe takes these gases (that turn into water) away from your property. These condensed gases are what is dripping from the condensate pipe.

So, whilst a condensate pipe can cause problems, it’s not causing the F22 fault on your Vaillant boiler.

Other Vaillant Fault Codes And Error


If your looking for the list of error codes relating to the Vaillant boiler then please read the article Vaillant Boiler Fault Codes And Cures