What does the Baxi Duo-tec F66 fault code mean?
The F66 fault code on a Baxi Duo-tec boiler indicates a problem with the central heating expansion vessel. This component is crucial for maintaining the correct pressure in the heating system and preventing damage due to excess pressure.
Common Causes
- Loss of Pressure: If the system pressure is too low, it can indicate a failure in the expansion vessel or a leak in the system.
- Bladder Failure: The diaphragm inside the expansion vessel may have ruptured, leading to a loss of its ability to absorb pressure fluctuations.
Can I fix it myself? (DIY)
While checking the system pressure can be done by yourself, it is recommended to call a Gas Safe Engineer for any repairs related to the expansion vessel, as it involves gas and safety regulations.
Estimated Repair Cost (2026 UK Prices)
The estimated cost for replacing the expansion vessel on a Baxi Duo-tec boiler is around £150 to £250. This includes parts and labour, reflecting the complexity of the job and the need for a qualified technician.