BoilerFaultCodesVaillant D.19 Fault Code
Also written as D19 — same fault.
The Vaillant D.19 fault code means: your boiler is currently running a check on its internal pump speeds to ensure it is circulating water as efficiently as possible.. It appears on 18 Vaillant models in our database.
Technical description: Operating modes of the two speed heating pump
What causes the Vaillant D.19 fault?
This is not a mechanical failure, but rather a temporary status where the boiler is adjusting its pump to the most efficient speed for your heating requirements. It occurs when the control board is testing the circulation to ensure water is moving through the heat exchanger at the correct rate. Once the boiler confirms the flow is optimal, the code will disappear and normal operation will resume.
This is more common in autumn when the heating is first turned back on after summer and the system is recalibrating for regular use.
DIY fix possible
No action is required as this is a status message rather than a faultMonitor the display to ensure it progresses to a standard temperature readingIf the code persists for a long period, restart the boiler using the power button
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.19 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax
- Combi Compact 242EB Repair: £120-250
- Combi Compact 282EB Repair: £180-£350
- 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
- ecoTEC plus System
- ecoTEC sustain
- Home System Repair: £0-80
Source
Vaillant D.19 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