BoilerFaultCodesGlow-worm Low water pressure LED flash Fault Code
Also written as LOWWATERPRESSURELEDFLASH — same fault.
The Glow-worm Low water pressure LED flash fault code means: your boiler has detected that there is not enough water in the heating system to operate safely.. It appears on 1 Glow-worm model in our database.
Technical description: Indicates insufficient system pressure or a faulty low water pressure switch.
What causes the Glow-worm Low water pressure LED flash fault?
This fault occurs when the water pressure inside your heating system drops below a safe level, preventing the boiler from firing up to protect the internal components. The most common reasons for this are a leak somewhere in the pipework or radiators, or simply needing to top up the system after bleeding air from your radiators.
This issue is frequently seen in autumn when homeowners turn their heating back on for the first time or bleed their radiators to prepare for winter.
DIY fix possible
Locate the filling loop (usually a silver flexible hose) underneath or near the boilerSlowly open the tap or taps on the filling loop to allow water into the systemMonitor the pressure gauge until it reaches between 1 and 1.5 bar, then close the taps fully
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Gas Safe Register →Glow-worm models that show the Low water pressure LED flash fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Low water pressure LED flash 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