BoilerFaultCodesGledhill 33 Fault Code
The Gledhill 33 fault code means: your boiler has detected that the water pressure in your heating system is currently too low for it to operate safely.. It appears on 1 Gledhill model in our database.
Technical description: REFLO_TOO_LO_ERROR
DIY fix possible
Locate the external filling loop, which is a flexible silver hose connected between two pipes under your boiler.Open the valves at both ends of the filling loop to allow cold mains water to enter the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone, typically between 1.0 and 1.5 bar.Close both valves firmly and ensure the flexible hose remains attached or capped as required.
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Gledhill models that show the 33 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Gledhill 33 fault code information on this page is sourced and cross-checked against the official Gledhill service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026