BoilerFaultCodesGlow-worm 0 8 Fault Code
Also written as 08 — same fault.
The Glow-worm 0 8 fault code means: your boiler has stopped working because the pipe that drains away excess liquid is blocked, likely due to debris or frozen water if it is cold outside.. It appears on 1 Glow-worm model in our database.
Technical description: Condensate drain becomes blocked. (Display will repeatedly flash '0' then '8')
What causes the Glow-worm 0 8 fault?
This fault occurs when the boiler's internal drainage system becomes backed up with liquid that can no longer escape. The most common reason is a blockage in the external pipe, often caused by a buildup of sludge or debris within the condensate trap itself. When the water level rises too high inside the unit, a safety sensor shuts the system down to prevent internal leaking or damage.
This fault is significantly more common during freezing winter weather, as the external drainage pipe can ice up and prevent water from leaving the boiler.
DIY fix possible
Check the white plastic pipe leading outside to see if the end is submerged in water or blocked by debris.If it is freezing weather, gently pour warm (not boiling) water over the external pipe to melt any ice blockages.Ensure any external collection tanks or 'soakaways' are not overflowing or backed up.
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Gas Safe Register →Glow-worm models that show the 0 8 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 0 8 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