BoilerFaultCodesSime 07 Fault Code
The Sime 07 fault code means: your boiler has detected that the water pressure inside the system is too low, preventing it from heating your home or water properly.. It appears on 5 Sime models in our database.
Technical description: ALARM 07
DIY fix possible
Locate the external filling loop (usually two silver flexible braided hoses underneath the boiler).Slowly open the valves on the filling loop to allow cold mains water to enter the system.Monitor the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar).Close both valves tightly to prevent over-pressurisation.
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Sime models that show the 07 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Sime 07 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