E125 High

Potterton E125 Fault Code

The Potterton E125 fault code means: your boiler has stopped working because water is not moving through the system correctly, which could be due to a blockage or a pump issue.. It appears on 12 Potterton models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Circulation Fault (Primary Circuit). Displayed if: i) Within 15 seconds of burner lighting water temperature hasn't changed by 1 degree. ii) Within 10 minutes of burner lighting water temperature twice exceeds selected temperature by 30 degrees.

What causes the Potterton E125 fault?

This fault occurs when the boiler detects that water is not moving around the internal system fast enough to carry heat away from the burner. The most common reasons are a seized internal pump that has failed to start or a build-up of sludge and debris blocking the narrow pipes within the main heat exchanger. When the water stays still, it overheats almost instantly, triggering a safety shutdown to prevent damage.

This issue often surfaces at the start of autumn when the heating is turned on for the first time after summer, as the pump can seize up during long periods of inactivity.

Typical repair cost £180-450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Potterton models that show the E125 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Potterton E125 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