BoilerFaultCodesGlow-worm F22 Fault Code
The Glow-worm F22 fault code means: your boiler has detected that there is not enough water pressure in the system to operate safely, which has caused it to shut down.. It appears on 10 Glow-worm models in our database.
Technical description: Low water pressure or No water in boiler
What causes the Glow-worm F22 fault?
This fault occurs when the water pressure inside your heating system drops below the minimum level required for the boiler to heat up safely. The most common reason is a slow leak from a radiator valve or pipework, though it can also happen if you have recently bled your radiators and didn't top the pressure back up.
This fault often appears when you turn your heating back on for the first time in autumn, as small leaks or air pockets may have developed during the months of inactivity.
DIY fix possible
Locate the external filling loop, which is usually a flexible silver hose with two small valves underneath or near the boiler.Slowly open both valves to allow water into the system while watching the pressure gauge.Close both valves tightly once the pressure gauge reaches between 1.0 and 1.5 bar.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the F22 fault code
Click a model for the full fault code list and model-specific repair notes.
- Flexicom 18sx Repair: £60-120
- Flexicom hx Repair: £60-120
- Flexicom sx Repair: £60-120
- Ultracom 2 CXI Repair: £60-120
- Ultracom 2 HXI Repair: £60-120
- Ultracom 24cx 30cx Repair: £60-120
- Ultracom 35 Store Repair: £60-120
- Ultracom cxi Repair: £60-120
- Ultracom hxi Repair: £60-120
- Xtramax HE Repair: £0-120
Source
Glow-worm F22 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026