F42 High

ECA F42 Fault Code

The ECA F42 fault code means: your boiler is unable to automatically refill itself with water, which could be due to low pressure in your home's water pipes or a faulty internal valve.. It appears on 3 ECA models in our database.

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.

Technical description: Water Filling (Auto) Not Completed (blocking) — water filling valve may have failed or mains water pressure insufficient; notify ECA authorised service
Typical repair cost £120-220 (including labour)

DIY fix possible

Check that your main property water stopcock is fully openEnsure there are no local water supply interruptions in your areaTry to manually reset the boiler by pressing the 'Reset' button to see if it triggers a re-fill

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ECA models that show the F42 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

ECA F42 fault code information on this page is sourced and cross-checked against the official ECA service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026