High
d6 on Worcester Bosch Highflow 550 CDi

Your boiler has detected that the internal water storage tank is overfilling, which forces the system to stop working to prevent internal flooding or water damage.

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

Internal heat bank overflow

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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