F22
FAULT CODE
Glow-worm
Low Water Pressure
Low Severity
DIY Check Possible
The system water pressure has dropped below the minimum required level. This is the modern equivalent of the older F9 code on newer Glow-worm models.
Step-by-Step Fix Guide
-
Step 1
Locate the filling loop (silver braided hose under the boiler)
-
Step 2
Slowly open both valves until pressure gauge reads 1.5 bar
-
Step 3
Close valves and reset the boiler
-
Step 4
If pressure drops again frequently, check for leaks or contact a Gas Safe engineer
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.