Low
D.25 on Vaillant Combi Compact 242EB

Your boiler is simply indicating that it has received a signal from an external smart thermostat or control unit to start providing hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Hot water activation via ebus control

DIY fix possible

Check your hot water tap is turned offEnsure your external thermostat or controller settings are correctNo action is required if hot water is currently being used

Find a Gas Safe engineer
Search the official register →

Related fault codes

D.22View →D.23View →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →