BoilerFaultCodesIdeal 4.11 Fault Code
Also written as 411 — same fault.
The Ideal 4.11 fault code means: your boiler has detected that the water pressure in the system is too low and needs to be topped up to work properly.. It appears on 8 Ideal models in our database.
Technical description: Low Water Pressure
What causes the Ideal 4.11 fault?
This fault occurs when the water level inside your central heating system drops below a safe threshold, often due to a small leak in a radiator valve or air escaping through the vents. Without enough water pressure, the boiler cannot safely circulate heat around your home and shuts down to prevent internal damage. The most common reason is the natural loss of pressure over time or after you have recently bled your radiators.
This issue is frequently seen in autumn when homeowners turn their heating back on for the first time after summer, revealing pressure losses that occurred while the system was idle.
DIY fix possible
Locate the filling loop (the flexible silver hose) underneath your boiler.Slowly open the blue-handled valves until you hear water entering the system.Watch the pressure gauge and close the valves tightly once the needle reaches 1.5 bar.
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Gas Safe Register →Ideal models that show the 4.11 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 4.11 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