Low
d.31 on Vaillant Home System

Your boiler is displaying a setting information code rather than a fault, indicating how the system manages its own water pressure levels.

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

Automatic filling device: 0=Manual, 1=Semi-automatic, 2=Automatic

DIY fix possible

No action is required as this is an advisory status codeIf system pressure is low, manually top up using the filling loopMonitor the pressure gauge to ensure it stays between 1 and 1.5 bar

Find a Gas Safe engineer
Search the official register →

Related fault codes

F.22View →F.73View →

Related guides you might find useful

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →