73:0 Low

Viessmann 73:0 Fault Code

Also written as 730 — same fault.

The Viessmann 73:0 fault code means: your boiler's hot water pump is scheduled to be running, but it may not be operating correctly or is being flagged for an advisory check.. 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: DHW circulation pump: ON according to time program

What causes the Viessmann 73:0 fault?

This is a status message rather than a mechanical failure, occurring when the boiler's internal clock triggers the secondary hot water pump to run. It indicates that the system is successfully moving hot water around your pipes so it is instantly available at your taps. You may see this code during your scheduled 'on' periods or if the pump has been manually boosted.

Typical repair cost £90-180 (including labour)

DIY fix possible

Check your hot water time program settings on the control panelEnsure the pump is not physically stuck or blockedReset the boiler to see if the advisory code clears

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Viessmann models that show the 73:0 fault code

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

Source

Viessmann 73:0 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