How much does it cost to fix Baxi error code 125?

Typical repair cost for the Baxi 125 fault is £150-£350 including labour.

125 High

Baxi 125 Fault Code

Q: What does the Baxi 125 fault code mean?

Your boiler has detected that water isn't moving through the system properly, which is causing it to overheat and shut down for safety.

The Baxi 125 fault code means: your boiler has detected that water isn't moving through the system properly, which is causing it to overheat and shut down for safety.. It appears on 26 Baxi models in our database.

Technical description: Water circulation fault

What causes the Baxi 125 fault?

This fault occurs when the boiler's internal sensors detect that the water temperature is rising too quickly because it isn't being moved away from the burner. The most common reason is a seized or failing pump, though it can also be caused by an airlock or a blockage in the system preventing the water from flowing. For your safety, the boiler shuts down immediately to prevent the heat exchanger from reaching dangerous temperatures.

This fault is frequently seen at the start of autumn when heating systems are turned back on after months of inactivity, which can cause the internal pump to seize.

Typical repair cost £150-£350 (including labour)

DIY fix possible

Check that your system pressure is between 1 and 1.5 bar on the pressure gaugeEnsure all radiator valves and isolation valves under the boiler are fully openBleed your radiators to remove any trapped air pockets

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Baxi models that show the 125 fault code

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

Source

Baxi 125 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026