BoilerFaultCodesSime E8 Fault Code
The Sime E8 fault code means: your boiler's internal water pressure is too low, meaning there is not enough water circulating to heat your home or provide hot water.. It appears on 2 Sime models in our database.
Technical description: TBD
DIY fix possible
Locate the external filling loop (a flexible metal or braided hose) connected to your boiler's pipeworkOpen the valves on the filling loop to allow cold mains water to enter the systemMonitor the pressure gauge on the boiler front until it reaches between 1.0 and 1.5 bar, then close the valves tightly
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Sime models that show the E8 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Sime E8 fault code information on this page is sourced and cross-checked against the official Sime service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026