BoilerFaultCodesVaillant d.81 Fault Code
Also written as D81 — same fault.
The Vaillant d.81 fault code means: this code is simply an information display showing the total number of hours your hot water system has been running; it is not a fault and your boiler is operating normally.. It appears on 26 Vaillant models in our database.
Technical description: Number of hot water system operating hours in h (Total) (ecoMAX 800)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like d.81: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Vaillant models that show the d.81 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax
- ecoFIT Pure 418
- ecoFIT Pure 425
- ecoFIT Pure 435
- ecoFIT Pure 825
- ecoFIT Pure 830
- ecoFIT Pure 835
- ecoMAX
- ecoMAX 613
- ecoMAX 618
- ecoMAX 622
- ecoMAX 635
- Ecomax Condensing 600/800 series
- ecoMAX System 612
- ecoTEC 65kW
- ecoTEC plus aquaPLUS
- ecoTEC sustain
- Home Combi
- Thermocompact
- Turbomax 824/828
- Turbomax Plus
- Turbomax Plus 824/828E
- Turbomax Plus 828
- Turbomax Plus 828 E
- Turbomax Plus VUW 242E
- Turbomax Plus VUW 242EH
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.
- Vaillant ecoFIT Pure 425 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant Ecomax Condensing 600/800 series manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026