How much does it cost to fix Vaillant error code P1?

Typical repair cost for the Vaillant P1 fault is £120-250 including labour.

P1 High

Vaillant P1 Fault Code

Q: What does the Vaillant P1 fault code mean?

Your boiler is currently running at its maximum gas setting, which is usually a sign that it is trying to heat up quickly or has detected an internal issue with the gas flow control.

The Vaillant P1 fault code means: your boiler is currently running at its maximum gas setting, which is usually a sign that it is trying to heat up quickly or has detected an internal issue with the gas flow control.. It appears on 1 Vaillant model in our database.

Technical description: Full gas rate

Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Vaillant models that show the P1 fault code

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

Thermocompact Repair: £120-250

Source

Vaillant P1 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