Boiler displays F22, with no heating or hot water, and the pressure gauge is near zero.

Safety: Do not run the boiler with no water; this can damage the heat exchanger.

User steps:

• Check the pressure gauge. If below approximately 0.8–1.0 bar (cold), open the filling loop valves and slowly fill the system to the recommended pressure (usually 1.0–1.5 bar). Close the valves afterwards.
• Bleed radiators to remove air, then re-check and adjust pressure.

If F22 persists:

• Inspect the system for visible leaks at radiators, valves, and under the boiler. Repair any leaks before topping up again.
• Check the water pressure sensor for blockage or failure and replace it if necessary.

After repair: Reset the boiler and confirm stable pressure and normal operation without F22.