Low Water Pressure - Your system needs topping up
Low Pressure
5 Minutes
Yes!
Free
The F22 error code indicates low water pressure in your central heating system. This is one of the most common boiler faults and is usually easy to fix yourself in just 5 minutes.
Your boiler needs the right amount of water pressure (typically between 1.0 and 1.5 bar) to circulate hot water around your radiators. When pressure drops below this level, the boiler displays F22 and shuts down for safety.
This is usually a simple DIY fix. You just need to top up the pressure using your boiler's filling loop. No engineer required!
Look at the pressure gauge on your boiler's front panel. On digital displays, pressure may be shown as a number. If it's below 1 bar (or in the red zone on analogue gauges), your system needs topping up.
Find the filling loop - this is usually a silver braided hose with two valves (or sometimes a single built-in key). It's typically located underneath the boiler or nearby on the pipework. Some newer Vaillant boilers have a built-in filling key instead.
Turn the filling loop valves anti-clockwise to open them (or insert and turn the filling key). Open them slowly - you'll hear water entering the system. If it has two valves, open both.
Keep watching the pressure gauge as water enters the system. When it reaches between 1.0 and 1.5 bar, stop adding water. Don't exceed 1.5 bar - too much pressure can cause other problems.
Close the filling loop valves firmly (clockwise) or remove the filling key. Then reset your boiler by pressing the reset button for 3-5 seconds. The F22 error should clear and the boiler should fire up.
If you find yourself topping up the pressure frequently (more than once a month), there's likely a leak in your system or a problem with the expansion vessel. This requires a Gas Safe engineer to diagnose and fix.
If you're constantly topping up, there may be a leak. Our Gas Safe engineers can find and fix it.
Common reasons for losing pressure:
Our Gas Safe engineers are available 24/7 across Harrow, London and surrounding areas.