BoilerFaultCodesYour boiler is not receiving enough gas to stay lit safely, which is preventing your heating and hot water from working.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Minimum gas pressure
What causes this fault?
This fault occurs when the incoming gas pressure drops below the minimum level required for the boiler to operate safely. The most common reasons are a blockage in the gas supply line, a failing gas valve within the boiler, or an issue with the external regulator on your gas meter.
This issue is more common during extreme cold snaps when high local demand for gas can cause a drop in network pressure, or when external regulators are prone to freezing.
DIY fix possible
Check that your gas emergency control valve (usually by the meter) is fully openIf you have a pre-payment meter, check that you have sufficient credit and the valve hasn't trippedCheck if other gas appliances in your home, like a hob, are working correctly to rule out a grid supply issue
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 426 — no call-out fees, no surprises.
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Ideal Systemiser SE is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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