BoilerFaultCodesGlow-worm 16 Fault Code
The Glow-worm 16 fault code means: your boiler has detected that gas is continuing to flow when it should have stopped, which is a significant safety concern.. It appears on 5 Glow-worm models in our database.
Technical description: GAS LEAK THROUGH THE SAFETY ELECTRIC VALVES: CHECK THE SAFETY ELECTRIC VALVE
What causes the Glow-worm 16 fault?
This fault occurs when the boiler's internal sensors detect that gas is still passing into the burner even after the system has commanded the flow to stop. The most common reason is that the seals inside the gas valve have become stuck or damaged, preventing it from closing fully, though a communication error from the main control board can also trigger this warning.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 16 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 16 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