High Lockout
AL41 on Vokera Syntesi 29

Your boiler has detected that the water pressure is too low to operate safely and has shut down to prevent damage.

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 fault

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 fire up. The most common reason is a small leak in the pipework or radiators, though it can also happen if you have recently bled your radiators without topping the water back up.

This fault is more common in autumn and winter when the heating is first turned on, as the increased demand can expose small leaks or reveal a loss of pressure 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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