How much does it cost to fix Vaillant error code F24?

Typical repair cost for the Vaillant F24 fault is £120-£350 including labour.

F24 High

Vaillant F24 Fault Code

Q: What does the Vaillant F24 fault code mean?

Your boiler has shut down because the water returning from your radiators has become too hot, usually due to a lack of water flow through the system.

The Vaillant F24 fault code means: your boiler has shut down because the water returning from your radiators has become too hot, usually due to a lack of water flow through the system.. It appears on 2 Vaillant models in our database.

Technical description: Central heating return t° >90°C

What causes the Vaillant F24 fault?

This fault occurs when the water returning to the boiler is nearly boiling, which usually means the heat isn't being carried away to your radiators quickly enough. The most common reason is a failing pump that can't circulate the water, or a blockage in the system pipework that is restricting the flow.

This fault is more common when the heating is first turned on after summer, as circulation pumps can often seize up after long periods of inactivity.

Typical repair cost £120-£350 (including labour)

DIY fix possible

Ensure all radiator valves (TRVs) are turned to the highest settingCheck that the boiler pressure is between 1.0 and 1.5 bar on the gaugeGently bleed your radiators to remove trapped air

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Vaillant models that show the F24 fault code

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

Source

Vaillant F24 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026