High
E04 on Warmflow Agentis External

Your boiler has detected that the water pressure is too low for it to operate safely, which often happens after bleeding radiators or if there is a small leak.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Low System Pressure — air lock, displaced NTC sensor, circulation problem, system leak, pressure loss after bleeding; check system pressure; verify corrosion inhibitor; consult if unresolved

From this model's manual
Verified against the Warmflow Agentis Internal installation & service manual, page 136.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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