BoilerFaultCodesRemeha E18 Fault Code
The Remeha E18 fault code means: your boiler has detected that the water inside is getting too hot because it isn't moving through the system quickly enough.. It appears on 3 Remeha models in our database.
Technical description: Flow temperature too high: check system flow and pump.
What causes the Remeha E18 fault?
This fault occurs when the heat generated by the burner cannot be transferred away from the boiler fast enough, causing the internal water temperature to spike safely out of range. The most common reasons are a failing circulation pump that isn't pushing water through the pipes, or a blockage caused by a buildup of sludge and debris within the system.
This issue is most frequently seen in autumn when heating is switched back on after a summer of inactivity, which can cause internal pump components to seize.
DIY fix possible
Check that at least two or three radiators have their valves turned fully openEnsure the external pump (if visible) is vibrating or hummingCheck that the system pressure gauge is between 1.0 and 1.5 barWait for the boiler to cool down and press the 'Reset' button
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Gas Safe Register →Remeha models that show the E18 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Remeha E18 fault code information on this page is sourced and cross-checked against the official Remeha service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026