The Vaillant boiler F22 fault code, explained

Boiler issues can leave you without hot water and switch off your central heating when you least expect it. Thankfully, modern Vaillant boilers use error codes to signal a fault. These give you a way to check the severity of the problem, and they make troubleshooting an easier process. A Vaillant boiler F22 fault code is among the most commonly searched online. This article guides you through what this code means, what you can potentially do about it, and when to contact a Gas Safe-registered engineer.

What does the Vaillant F22 error code stand for?

An F22 fault happens when there’s too little water pressure for your boiler to fire up. That’s why, if you’re looking at a Vaillant F22 fault code, your boiler is probably ‘locked out’, and there’s no hot water coming from your taps or shower. You’ll also notice that your radiators won’t be warming up as expected.

In addition to this code, you may notice that a number such as 0.3 flashes up on your boiler’s display. This is the pressure level inside the system, which should normally be around 1.5 bar depending on the model. You could also check the pressure gauge if you have one to corroborate the problem.

Tip: The recommended pressure level can vary between Vaillant boiler models. Please check your boiler’s manual to find this information.

Why does my boiler have low water pressure?

Boilers can lose pressure for several reasons. These include age, leaks in the pipework or a damaged expansion vessel or pressure release valve. You may also notice pressure drops if you’ve recently bled your radiators. However, most Vaillant boiler F22 faults happen because air gets into the system. As such, you may have to top the pressure up every six months or so.

Note that this is a gradual drop and not something that occurs overnight. If you have a sudden loss of pressure or have to top the boiler’s pressure level up every few weeks, it means there’s an underlying issue.

How can I correct pressure issues in my Vaillant boiler?

You can try to repressurise your boiler if you’re confident that you can do it correctly and safely. To do this, you’ll need to turn the valves connected to each end of the boiler’s filling loop. This may remove the F22 code and restore your system to normal, but please note that you shouldn’t have to do this more than once or twice a year.

Check your display to make sure it’s an F22 code
Find the two valves, usually located beneath the boiler
Rotate the right valve 90 degrees, then slowly rotate the left valve
Watch the boiler’s display to ensure the pressure bar rises
Once the pressure’s between 1.2 and 1.5 bar, close both valves
You may have to reset your boiler if the F22 code still appears

This whole process should only take a few seconds. Make sure you close both valves once the pressure reaches the ideal level, preferably no higher than 1.5 bar for a cold system. This is because your boiler will raise the pressure once it fires up, so you can expect your display to read closer to 2 bar. If it gets higher than 2.5 bar, you may have over-pressurised the system.

Tip: Increased the pressure by too much? Don’t panic! You can reduce it by bleeding your radiators and checking the boiler pressure after bleeding each one. We have a guide on how you can bleed a radiator yourself, but if you prefer, you can always get us to do it for you. We could also inspect your boiler for underlying issues.

Below: An example of a filling loop underneath a combi boiler. If you have a system or heat only boiler, your filling loop may be connected to the pipework or attached to an external expansion vessel.

What if the F22 comes back in a week or two?

If the code returns soon after topping the pressure up, it’s time to call in a Gas Safe-registered engineer. They will check the boiler for damaged components, and if they find the source of the problem, they can then provide the boiler repairs you need. If your engineer can’t find a fault on the boiler, a leak is the most likely issue.

We have gas services engineers who are skilled and equipped for central heating leak detection. If they can’t find a fault on your boiler, or a leak on the exposed parts of your central heating system, they can start the non-invasive detection process on concealed parts of your system right away. They can trace central heating leaks buried beneath solid floors. This avoids booking another appointment. Please note, our leak detection service is performed at a different half-hour rate to gas work.

Important! You should never try to make the repairs yourself. Doing so could cause major damage to your boiler, and you could increase the risk of carbon monoxide poisoning. Gas Safe heating engineers are trained to work with heating systems, and always within HSE regulations.

How can I avoid getting a Vaillant boiler F22 error code?

Boiler issues can happen suddenly and for many reasons, so it’s hard to safeguard against them – and this applies to all makes and models. The best thing you can do is keep up to date with your servicing your gas boiler. A yearly boiler service is expected by home insurance companies, and without it, you could lose your manufacturer’s guarantee.

Did you know? Annual servicing may reduce your gas usage by up to 30%. Your engineer can check that your boiler’s set to the right temperature and that it’s burning gas efficiently. If it isn’t, they can make some tweaks to optimise its performance.

Aspect can get to the heart of any Vaillant boiler problem, whether it’s due to insufficient water pressure, a loose connection or a broken part. We’re even members of the Vaillant Advance approved installer scheme, so we’re able to provide the unique advice, installation and maintenance work you’d expect from a Vaillant specialist. Whatever the fault code, we’ll fix the problem as quickly as possible, for a warm and energy-efficient home all year round.