BoilerFaultCodesIntergas E04 Fault Code
The Intergas E04 fault code means: your boiler has detected that the water pressure is too low for it to run safely, or there is a blockage preventing water from circulating.. It appears on 6 Intergas models in our database.
Technical description: Water pressure too low or no water flow
What causes the Intergas E04 fault?
This fault occurs when the boiler detects that there isn't enough water pressure in the system to operate safely, or the water isn't moving through the unit correctly. The most common reason is a gradual loss of pressure through small leaks or after bleeding your radiators, but it can also be triggered by a faulty pump that isn't pushing water around the circuit.
This issue often appears when you first turn the heating back on for autumn, as the system has been dormant and may have lost pressure over the summer months.
DIY fix possible
Check the pressure gauge on your boiler or under the sink; it should be between 1.0 and 1.5 bar.Locate the filling loop (a flexible silver hose) and slowly open the valves until the pressure reaches 1.2 bar.Ensure all radiator valves are open and your external pump (if applicable) is running.
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Gas Safe Register →Intergas models that show the E04 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Intergas E04 fault code information on this page is sourced and cross-checked against the official Intergas service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026