BoilerFaultCodesGlow-worm F.75 Fault Code
Also written as F75 — same fault.
The Glow-worm F.75 fault code means: your boiler has failed to detect a rise in pressure when the pump started, meaning it cannot safely circulate water to heat your home.. It appears on 6 Glow-worm models in our database.
Technical description: Pressure sensor fault
What causes the Glow-worm F.75 fault?
This fault occurs when the boiler's internal computer doesn't see a small 'jump' in water pressure that should happen every time the pump kicks in. The most common reasons are a sensor blocked with debris or a failing pump that isn't moving the water with enough force to be detected.
This fault is more frequent in autumn when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.
DIY fix possible
Check the pressure gauge on the front of the boilerIf the pressure is below 1.0 bar, use the filling loop to top it up to 1.5 barPress the 'Reset' button (indicated by a flame with a cross through it) to restart the boiler
Find a Gas Safe engineer
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Gas Safe Register →Glow-worm models that show the F.75 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F.75 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