What does the Glow-worm Energy F79 fault code mean?
The F79 fault code on the Glow-worm Energy boiler indicates a problem with the domestic hot water (DHW) expansion vessel. This fault typically arises when the vessel is either waterlogged or has lost its pre-charge pressure, affecting the boiler’s ability to maintain hot water pressure.
Common Causes
- Waterlogged Expansion Vessel: Over time, the expansion vessel can fill with water, preventing it from absorbing pressure changes effectively.
- Loss of Pre-charge Pressure: The pre-charge pressure in the expansion vessel may drop, leading to inadequate performance and triggering the fault code.
Can I fix it myself? (DIY)
It is advisable to call a Gas Safe Engineer to address this issue, as it involves working with pressurised systems and potentially gas components. Attempting to fix it yourself could pose safety risks.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for addressing the F79 fault code is around £150 to £250. This includes the cost of a new expansion vessel and labour, as it requires professional installation to ensure safety and compliance with regulations.