BoilerFaultCodesKeston No water flow lockout Fault Code
Also written as NOWATERFLOWLOCKOUT — same fault.
The Keston No water flow lockout fault code means: your boiler has stopped working because it cannot detect water moving through the system to keep it cool and functioning safely.. It appears on 1 Keston model in our database.
Technical description: No water flow lockout
DIY fix possible
Check that your boiler pressure gauge is between 1.0 and 1.5 bar.Ensure all radiator valves and isolation valves under the boiler are fully open.Gently bleed your radiators to remove any trapped air pockets.Restart the boiler using the reset button once pressure is confirmed.
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Keston models that show the No water flow lockout fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston No water flow lockout 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 7 July 2026