BoilerFaultCodesWhat the manual says
Manufacturer manualInsufficient system water pressure
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 operate safely. The most common reason is a slow leak from a radiator valve or pipework, but it can also happen if you have recently bled your radiators and haven't topped the system back up.
This issue is frequently seen at the start of autumn when homeowners turn their heating back on for the first time or bleed their radiators after 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.
Avoid the next call-out bill
A cover plan would handle faults like AL40: no call-out fees, no surprise bills.
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Related fault codes
All 22 fault codes on the Mynute 23E
Seeing a different code? Every code this model can display, in one place.
Related guides you might find useful
Boiler keeps losing pressure
Six most common causes of dropping pressure.
Read →Hot water works but heating does not
On a combi it is usually the diverter valve. On a system boiler, the motorised valve.
Read →What pressure should my boiler be?
1 to 1.5 bar when cold on most UK boilers, from the manuals.
Read →