High Lockout
E125 on Baxi 600 Combi (range)

Your boiler has detected that hot water isn't moving through the system properly, which is likely caused by a blockage or a pump issue.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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).

What causes this fault?

This fault occurs when the internal sensors detect that water is getting too hot too quickly because it isn't moving away from the heat exchanger. The most common reasons are a seized circulation pump, a blockage caused by sludge buildup, or an air lock trapped within the pipework.

This issue often appears during the first cold snap of autumn when a pump that has been idle all summer fails to restart.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E110View →

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