D.81 Low

Vaillant D.81 Fault Code

Also written as D81 — same fault.

The Vaillant D.81 fault code means: this is an information code rather than a fault, showing you the total number of hours your boiler has spent heating up your water.. It appears on 30 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: Operating hours hot water generation

What causes the Vaillant D.81 fault?

This code is not caused by a breakdown or failure, but is simply a recorded log of the appliance's usage. It appears when the control board reaches a specific interval or when a user accesses the diagnostics menu to check the system's workload. It acts like a mileage counter on a car, tracking how much work the boiler has done specifically for your taps and showers.

DIY fix possible

Press the 'Back' or 'i' button to exit the status menuMonitor your boiler for any actual fault codes starting with 'F'No action is required as this is a normal operational reading

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Vaillant models that show the D.81 fault code

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

Source

Vaillant D.81 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