High Lockout
S.41 on Vaillant ecoTEC exclusive

Your boiler has too much water in the system, which is causing high pressure and has triggered a safety shutdown to protect the components.

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

Water pressure too high: Water pressure > 2.8 bar

What causes this fault?

This fault occurs when the internal water pressure exceeds safe operating limits, often because the filling loop used to top up the system has been left slightly open or is leaking. It can also be caused by a failure in the expansion vessel, which is the part responsible for managing the natural pressure increase that happens when water heats up.

This issue often appears at the start of autumn when homeowners turn their heating back on after a long break, causing the water to expand and reveal underlying pressure problems.

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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