BoilerFaultCodesIdeal 426 Fault Code
The Ideal 426 fault code means: your boiler is not receiving enough gas to stay lit safely, which is preventing it from heating your home or water.. It appears on 2 Ideal models in our database.
Technical description: Minimum gas pressure
What causes the Ideal 426 fault?
This fault occurs when the boiler detects that the incoming gas supply is too weak to maintain a stable flame. The most common reason is a blockage or mechanical failure in the gas valve, but it can also be caused by an external issue with your gas meter or its regulator. When the pressure drops below a safe threshold, the boiler shuts down as a safety precaution to prevent unstable combustion.
This fault is more common during extreme cold spells, as high demand on the gas grid or freezing of external gas regulators can cause supply pressures to drop.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Ideal models that show the 426 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 426 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026