Filling Low

Viessmann Filling Fault Code

Also written as FILLING — same fault.

The Viessmann Filling fault code means: your boiler is currently in the process of being filled with water, and the control system is waiting for the pressure to reach the correct level before it can start working again.. It appears on 5 Viessmann models in our database.

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: Whilst filling is in progress (weather-compensated control unit)

DIY fix possible

Locate the filling loop (a flexible silver hose) underneath your boiler or near your pipework.Gradually open the valves on the filling loop to allow water into the system.Monitor the pressure gauge on the front of the boiler until it reaches the green zone (typically between 1.0 and 1.5 bar).Close both valves firmly once the pressure is correct.

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Viessmann models that show the Filling fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Viessmann Filling fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026