Seeing that dreaded F22 fault code on your Vaillant boiler? Take a deep breath—this common Vaillant F22 error is something many homeowners encounter, and in most cases, you can fix this Vaillant boiler F22 fault code yourself. Let’s get your heating system back up and running through these quick DIY fixes in minutes.
What does the Vaillant F22 Fault Code Mean?
The Vaillant F22 fault code on your Vaillant boiler means one simple thing: low water pressure in the system.
Think of your central heating system like the circulatory system in your body. Your Vaillant boiler needs good water pressure to push hot water through all those pipes and radiators in your heating system. When the water pressure in the system drops below about 0.5-1.0 bar, your Vaillant boiler displays the F22 error code and goes into “lockout mode”,—shutting down to prevent damage to your boiler components.
How to Check Your Boiler Pressure When You Have an F22 Fault Code
Step 1: Find the Pressure Gauge on Your Vaillant Boiler
Look for either:
- A round pressure gauge on the front of your Vaillant boiler
- Or on newer Vaillant boiler models, press the “i” or menu button to see the digital pressure reading
Step 2: Check What the Pressure Gauge is Showing
Here’s what the readings on your Vaillant boiler mean:
- Below 1.0 bar: The water pressure is too low — that’s why you’re seeing the F22 fault code
- 1.0-1.5 bar: Perfect pressure for your boiler when it’s cold
- 1.5-2.0 bar: Ideal pressure when the central heating system is hot and running
- Above 2.5 bar: Pressure is too high (that’s a different boiler fault code)
How to fix the Vaillant F22 fault code yourself
Most F22 error codes on a Vaillant boiler can be fixed in about 5 minutes with no specialized tools. Here’s how to fix the F22 fault code:
Fix an F22 Fault by Topping Up Your Boiler
- Turn your Vaillant boiler off and let it cool down
- Find the filling loop (usually a flexible silver or black hose underneath the boiler)
- Open both valve handles slowly by turning them counter clockwise
- Listen for water entering your central heating system
- Watch the pressure gauge climb back up to around 1.5 bar
- Close both valves firmly when the pressure reaches 1.5 bar
- Press the reset button on your Vaillant boiler
That’s it! Your Vaillant boiler should reset and start working again. If the F22 code persists, try pressing the reset button once more after ensuring the pressure is at 1.5 bar.
Got a Keyed Filling System on Your Vaillant Boiler?
Some Vaillant boiler models use a special key for topping up:
- Insert the key into the filling port on your Vaillant boiler
- Turn slowly while watching the pressure in your boiler rise to around 1.5 bar
- Remove and store the key somewhere safe
Common Causes of the F22 fault on Vaillant Boilers
Your Vaillant boiler didn’t lose water pressure just to annoy you! Here are the common causes of the F22 fault:
1. A Leak in Your Heating System
Even tiny leaks can cause pressure drops over time. Check around your radiators, pipe joints, and valves for damp patches or water marks. Sometimes leaks can be hidden inside walls or under floors, making them harder to locate and fix the leak.
2. Recently Bled Your Radiators?
When you release air from radiators, you also lose some water, which can trigger an F22 fault code due to low water pressure in the system.
3. Faulty Pressure Relief Valve
This safety valve on your Vaillant boiler sometimes develops faults and releases water when it shouldn’t, causing a drop in water pressure.
4. Problems with the Expansion Vessel
This component in your Vaillant boiler helps manage pressure changes but can sometimes fail, causing the F22 error code to appear.
5. Faulty Water Pressure Sensor
Sometimes the issue with your Vaillant boiler isn’t the actual pressure but the water pressure sensor that measures it. A defective pressure sensor or pump can trigger the F22 fault code even when the pressure is normal.
When to Contact a Gas Safe Engineer to Fix Your Vaillant Boiler
While the Vaillant F22 error code is often simple to fix yourself, there are times when you need a Gas Safe-registered heating engineer:
- Pressure drops again shortly after topping up your Vaillant boiler
- You can see a leak in your central heating system, but can’t access or fix it
- The F22 error code returns after resetting your Vaillant boiler
- Pressure won’t increase even after topping up
- Your boiler is still under warranty (don’t risk voiding it!)
A qualified heating engineer can find hidden leaks in your central heating system, check the expansion vessel, replace faulty parts like the pressure sensor or pump, and make sure your Vaillant boiler is working correctly and safely.
Prevent Future Vaillant F22 Error Codes with These Tips
1. Regular Boiler Pressure Checks
Just a quick look at your pressure gauge once a month can catch issues before they cause your boiler to shut down with an F22 fault.
2. Annual Boiler Service
Regular Vaillant boiler service by a Gas Safe engineer keeps everything running smoothly and helps catch potential issues before they leave you without heat or hot water.
3. Check the Pressure After Bleeding the Radiators
Remember to check your boiler pressure afterwards—bleeding radiators often requires topping up your boiler to prevent the F22 error.
4. Fix Leaks Promptly
Even small leaks in your heating system can lead to water pressure problems over time and trigger the F22 fault code on your Vaillant boiler.
The Bottom Line
The F22 fault code on your Vaillant boiler is simply its way of saying, “I need more water pressure to function safely!” In most cases, you can fix the Vaillant F22 error by topping up the system yourself using the filling loop.
Keep an eye on that pressure gauge, and remember—proper maintenance of your Vaillant boiler prevents those frustrating moments when boiler error codes appear and leave you without heating.
Still having trouble after trying these steps to fix the F22 fault code? Contact a Gas Safe registered engineer who can help locate and fix the leak or other issues causing your Vaillant boiler problem.
FAQs
No—the reset won’t work until the water pressure in the system is back to normal at around 1.5 bar!
Your Vaillant boiler indicates low water pressure with the F22 code because you likely have a leak somewhere in your central heating system, or issues with your expansion vessel or pressure relief valve.
The low pressure itself isn’t dangerous, but your Vaillant boiler displays the F22 error code and shuts down to protect itself—leaving you without hot water and heating.
Monthly checks of your pressure gauge and after bleeding radiators will help you avoid encountering the F22 fault code.
If your Vaillant boiler is over 10 years old and constantly having pressure issues with F22 error codes, a new boiler with better pressure management could save you money on both boiler repairs and energy bills in the long run.
