BoilerFaultCodesPotterton 118 Fault Code
The Potterton 118 fault code means: your boiler has stopped working because the water pressure inside the heating system has dropped below the minimum level required to operate safely.. It appears on 3 Potterton models in our database.
Technical description: Primary System Water Pressure Too Low
DIY fix possible
Locate the external filling loop, which is a flexible braided hose connected to two valves under your boiler.Open the valves slowly to allow mains water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close both valves firmly and ensure the filling loop is disconnected if it is a removable type.
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Potterton models that show the 118 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton 118 fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
- Potterton Assure manual (PDF)
- Potterton Performa 24i HE manual (PDF)
- Potterton Promax Ultra Combi ErP manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026