Vaillant boiler showing F22
F22 on a Vaillant means low water pressure. Most of the time you can fix it yourself in a couple of minutes, free.
What it actually means
F22 is Vaillant's low water pressure fault. The boiler has noticed there is not enough water in the heating circuit and has shut down to protect itself.
It is one of the most common boiler faults in the UK and usually the cheapest: the fix is often just topping the pressure back up.
Try this first, before you spend a penny
- 1
Find the pressure gauge
On the front of the boiler. If the needle or reading is below 1 bar, low pressure is your problem.
- 2
Find the filling loop
A small flexible hose or built-in valve under the boiler, usually with one or two small taps or levers.
- 3
Top up slowly
Open the valve(s) gently until the gauge reads between 1 and 1.5 bar, then close them firmly. You will hear water moving. Do not go above 2 bar.
- 4
Reset the boiler
Press the reset button. The fault should clear and the boiler should fire up.
When it is a pro job
If the pressure drops again within days, water is going somewhere: a small leak on a radiator valve or pipework, or an internal part like the expansion vessel. That diagnosis and fix is an engineer job.
Gas Safe registered heating engineer
Typical UK range for finding and fixing a pressure loss, from a simple valve reseal to an expansion vessel recharge. A repeat top-up costs you nothing.
£90 to £250
Related