How much does it cost to fix Potterton error code E125?

Typical repair cost for the Potterton E125 fault is £180-450 including labour.

E125 High

Potterton E125 Fault Code

Q: What does the Potterton E125 fault code mean?

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.

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.

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.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like E125: no call-out fees, no surprise bills.

Approved partner

Domestic Appliance Guard

Unlimited call-outs, 24/7 helpline, no price-hike promise

Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

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 7 July 2026