How much does it cost to fix Vaillant error code Er.15?

Typical repair cost for the Vaillant Er.15 fault is £150-250 including labour.

Er.15 Medium

Vaillant Er.15 Fault Code

Q: What does the Vaillant Er.15 fault code mean?

Your boiler is struggling to detect when you turn on a hot tap, which means you may have no hot water or the water temperature might stay cold.

Also written as ER15 — same fault.

The Vaillant Er.15 fault code means: your boiler is struggling to detect when you turn on a hot tap, which means you may have no hot water or the water temperature might stay cold.. It appears on 2 Vaillant models in our database.

Technical description: Aqua sensor

Typical repair cost £150-250 (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 Er.15 fault code

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

Thermocompact Repair: £150-250
Turbomax Pro 28 2E Repair: £150-250

Source

Vaillant Er.15 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