What does the Vaillant ecoFIT pure F42 fault code mean?
The F42 fault code on the Vaillant ecoFIT pure indicates a problem with the expansion vessel, which is responsible for maintaining system pressure and absorbing excess water expansion. A faulty expansion vessel can lead to pressure fluctuations and potential system failure if not addressed.
Common Causes
- Loss of Air Pressure: The air pressure within the expansion vessel may have dropped, leading to insufficient capacity to absorb expansion.
- Water Leakage: A rupture or leak in the expansion vessel can cause water to enter the air chamber, rendering it ineffective.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as working with the boiler’s pressure system can be dangerous. Attempting to fix it yourself may lead to further complications or safety hazards.
Estimated Repair Cost (2026 UK Prices)
The estimated cost for replacing a faulty expansion vessel is around £200 to £300, including parts and labour. This estimate reflects the complexity of the repair and the need for a qualified engineer to ensure safety and compliance with regulations.