Hot water demand indicator Low

Vaillant Hot water demand indicator Fault Code

Also written as HOTWATERDEMANDINDICATOR — same fault.

The Vaillant Hot water demand indicator fault code means: your boiler is working exactly as it should and is simply confirming that it has received your request to heat water for your tap or shower.. It appears on 3 Vaillant models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: The hot water demand indicator will illuminate when a hot tap is turned on and water is drawn at a high rate.

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 Hot water demand indicator fault code

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

Source

Vaillant Hot water demand indicator 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 7 July 2026