Boiler shows F22, no heating or hot water, pressure gauge low

Safety: Never run the boiler with no water; this can destroy the heat exchanger.

• Check pressure: If below 0.5 bar, top up via the filling loop to 1.0–1.5 bar.
• Bleed and recheck: Bleed radiators, then recheck and adjust pressure.
• Leak search: Inspect all visible pipework, radiators, and the boiler for signs of water loss. Check the pressure relief valve discharge pipe outside.
• Pressure sensor: If pressure is correct but F22 remains, the water pressure sensor may be stuck or faulty and should be replaced.