BoilerFaultCodesWarmhaus E03 Fault Code
The Warmhaus E03 fault code means: your boiler has too much water in the system, causing it to shut down to prevent damage from excessive pressure.. It appears on 1 Warmhaus model in our database.
Technical description: High water pressure due to excessive water pressure or safety valve error
What causes the Warmhaus E03 fault?
This fault occurs when the water pressure inside your heating system exceeds the safe operating limit. The most common reason is that the filling loop was left slightly open after topping up the system, or the internal expansion vessel has lost its air charge and can no longer balance the pressure changes as the water heats up. In some cases, a leaking internal component might be allowing fresh mains water to constantly enter the system.
This fault often appears when you first turn the heating back on for autumn, as the expansion of heating cold water can push an already high-pressure system over the safety limit.
DIY fix possible
Check that the filling loop valves are fully closedBleed water from a radiator using a bleed key to reduce pressureMonitor the pressure gauge to ensure it returns to between 1.0 and 1.5 barReset the boiler once the pressure is stabilised
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Gas Safe Register →Warmhaus models that show the E03 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Warmhaus E03 fault code information on this page is sourced and cross-checked against the official Warmhaus service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026