High
F.22 on Vaillant ecoTEC Pro 24

Your boiler has switched itself off because the water pressure has dropped too low to operate 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.

What the manual says

Manufacturer manual

The filling pressure falls below 0.05 MPa (0.5 bar) and the product switches off.

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the water pressure inside your heating system drops below a safe working level, causing the boiler to shut down to prevent internal damage. 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 code is frequently seen at the start of autumn when homeowners turn their heating back on for the first time after summer, revealing pressure losses that occurred while the system was idle.

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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