E12 High

Baxi E12 Fault Code

The Baxi E12 fault code means: your boiler has detected that water is not circulating correctly through the system, preventing it from heating up safely.. It appears on 25 Baxi 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: Differential water flow switch fault (still open).

What causes the Baxi E12 fault?

This fault occurs when the boiler's internal sensors detect that water isn't moving through the unit quickly enough to carry heat away safely. The most common reasons are a seized circulation pump, a blockage in the pipework, or a failure in the switch that monitors water flow. Because the heat cannot exit the boiler, the system shuts down to prevent the internal components from overheating.

This issue frequently appears during the first cold snap of autumn when a pump that has been idle all summer fails to restart or is hindered by settled debris.

Typical repair cost £120-280 (including labour)

DIY fix possible

Check that your boiler pressure is between 1.0 and 1.5 bar on the gaugeEnsure all radiator valves and isolation valves under the boiler are fully openBleed your radiators to remove any trapped air pocketsReset the boiler by turning the selector switch to 'R' for five seconds

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Baxi models that show the E12 fault code

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

Source

Baxi E12 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