BoilerFaultCodesKeston E26 Fault Code
The Keston E26 fault code means: your boiler is struggling to keep its flame lit, which often happens because the drainage pipe is blocked or frozen, or there is an issue with the air supply.. It appears on 9 Keston models in our database.
Technical description: Flame drop out – check for obstruction of the flue and/or air terminals, blockage/freezing of the drain pipe or a low gas supply (LPG).
What causes the Keston E26 fault?
This fault occurs when the boiler's internal computer detects that the flame has unexpectedly gone out during operation. The most common reason is that waste water cannot escape the unit due to a blockage in the drainage pipe, which causes the system to flood and extinguish the burner. It can also be caused by a lack of fresh air reaching the boiler or an unstable gas supply preventing a consistent flame.
This fault is specifically common during freezing winter temperatures, as the external condensate drainage pipe is prone to icing up and backing up the system.
DIY fix possible
Check the white plastic condensate pipe outside for signs of ice or blockages.If frozen, gently pour warm (not boiling) water over the pipe to thaw it.Ensure the external flue terminal is not obstructed by debris or garden foliage.
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Gas Safe Register →Keston models that show the E26 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston E26 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026