BoilerFaultCodesPotterton 26 Fault Code
The Potterton 26 fault code means: your boiler has switched itself off because the water pressure is too low or the pump that moves water around your radiators isn't working correctly.. It appears on 4 Potterton models in our database.
Technical description: Fault on Pump or Low System Pressure
What causes the Potterton 26 fault?
This fault occurs when the boiler detects that there isn't enough water pressure to safely operate or that water isn't being pushed through the internal heat exchanger. The most common reason is a simple drop in system pressure, but it can also be triggered if the pump has seized or failed due to age. If the water cannot move, the boiler shuts down to prevent the internal components from overheating.
This issue is frequently seen in autumn when the heating is turned on for the first time after summer, as pump components can seize during long periods of inactivity.
DIY fix possible
Locate the pressure gauge on the front of the boiler to see if it is below 1 bar.Find the filling loop (usually a silver braided hose with two small valves) underneath the boiler.Slowly open both valves until you hear water entering and the gauge reaches between 1 and 1.5 bar, then close them tightly.
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Gas Safe Register →Potterton models that show the 26 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton 26 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