BoilerFaultCodesVaillant 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 6 Vaillant models in our database.
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
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →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 27 April 2026