BoilerFaultCodesMain E117 Fault Code
The Main E117 fault code means: your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.. It appears on 1 Main model in our database.
Technical description: System water pressure fault
DIY fix possible
Locate the external filling loop, which is usually a small silver braided hose with one or two valves located underneath your boiler.Gradually open the valve(s) to allow mains water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close the valves tightly to stop the flow of water and check if the error code clears.
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Gas Safe Register →Main models that show the E117 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main E117 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026