High Lockout
F.22 on Vaillant ecoTEC

Your boiler has stopped working because the water pressure is too low for it to run safely.

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

insufficient water pressure in the heating system

What causes this fault?

This fault occurs when the water level inside your central heating system drops below the minimum level required to operate. 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 haven't topped the pressure back up.

This issue is more frequent in autumn when homeowners turn their heating back on for the first time or bleed their radiators to prepare for winter.

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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