BoilerFaultCodesVaillant D.36 Fault Code
Also written as D36 — same fault.
The Vaillant D.36 fault code means: your boiler is having trouble measuring the flow of hot water, which could mean your taps don't get as hot as they should or your hot water fluctuates.. It appears on 18 Vaillant models in our database.
Technical description: Hot water flow sensor
What causes the Vaillant D.36 fault?
This fault occurs when the internal sensor responsible for tracking how much water is moving through the system fails to send a clear signal to the main control board. The most common reason is that the sensor's internal components have worn out or become blocked by debris, preventing it from accurately telling the boiler to fire up for hot water.
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 →Vaillant models that show the D.36 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £120-210
- Combi Compact 242EB Repair: £120-210
- Combi Compact 282EB Repair: £120-£210
- ecoTEC plus
- ecoTEC Plus 615
- ecoTEC Plus 620
- ecoTEC Plus 625
- ecoTEC Plus 630
- ecoTEC Plus 635
- ecoTEC Plus 65
- ecoTEC Plus 832
- ecoTEC Plus 836
- ecoTEC Plus 840
- ecoTEC Plus 938
- ecoTEC plus Regular Repair: £120-£220
- ecoTEC plus System
- ecoTEC sustain
- Home System
Source
Vaillant D.36 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