High
11 on Glow-worm Xtrafast 120

Your boiler is struggling to circulate water properly because the internal pump is jammed or blocked, meaning it cannot effectively move heat to your radiators or taps.

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.

What the manual says

Manufacturer manual

Pump blockage

From this model's manual
Verified against the Glow Worm Xtrafast 96 installation & service manual, page 29.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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