t Low

Pro t Fault Code

Also written as T — same fault.

The Pro t fault code means: your boiler is currently heating up a small internal reservoir of water so that hot water is available instantly when you turn on the tap.. It appears on 3 Pro 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 preheat.
Typical repair cost £0 (including labour)

DIY fix possible

No action is required as this is a normal operating mode.If you wish to save energy, you can turn off the comfort/preheat function using the control dial.Check your user manual if you want to schedule the preheat times.

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Pro models that show the t fault code

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

Source

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

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026