BoilerFaultCodesMain 27 Fault Code
The Main 27 fault code means: your boiler is struggling because it either cannot circulate water correctly or there is not enough water pressure inside the system to operate safely.. It appears on 5 Main models in our database.
Technical description: Fault on Pump or Low System Pressure
DIY fix possible
Check the system pressure gauge on the front of the boiler; if it is below 1 bar, locate the filling loop.Open the filling loop valves to top up the system until the needle reaches 1.5 bar, then ensure the valves are tightly closed.Restart the boiler to see if the fault clears.
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Main models that show the 27 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main 27 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 7 July 2026