High Lockout
F22 on Glow-worm Flexicom sx

Your boiler has detected that there is not enough water pressure in the system to operate safely, which has caused it to shut down.

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

Low water pressure or No water in boiler

What causes this fault?

This fault occurs when the water pressure inside your heating system drops below the minimum level required for the boiler to heat up safely. The most common reason is a slow leak from a radiator valve or pipework, though it can also happen if you have recently bled your radiators and didn't top the pressure back up.

This fault often appears when you turn your heating back on for the first time in autumn, as small leaks or air pockets may have developed during the months of inactivity.

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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