BoilerFaultCodesPotterton 27 Fault Code
The Potterton 27 fault code means: your boiler has detected that there is not enough water pressure or the pump isn't circulating water through the system properly.. It appears on 4 Potterton models in our database.
Technical description: Fault on Pump or Low System Pressure
What causes the Potterton 27 fault?
This fault occurs when the boiler's internal sensors detect that water isn't moving through the heat exchanger as it should, which can cause the unit to overheat. The most common reasons are that the water pressure has dropped too low for the system to operate, or the internal pump has seized or failed. Occasionally, a large air bubble trapped inside the pipework can also block the flow and trigger this error.
This issue is frequently seen in autumn when the heating is turned back on for the first time, as pumps can seize after being idle over the summer.
DIY fix possible
Check the pressure gauge on the front of the boiler; it should ideally be between 1 and 1.5 bar.If the pressure is too low, use the filling loop valves underneath the boiler to top it up slowly.Bleed any trapped air from your radiators and then re-check the pressure gauge.
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Gas Safe Register →Potterton models that show the 27 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton 27 fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026