What does the Glow-worm Ultimate F81 fault code mean?
The F81 fault code on the Glow-worm Ultimate indicates an issue with the domestic hot water (DHW) flow switch. This typically means that the boiler is unable to detect water flow, which can prevent hot water from being produced.
Common Causes
- Blocked Flow Switch: Debris or limescale buildup can obstruct the flow switch, preventing it from functioning properly.
- Faulty Flow Switch: The flow switch itself may be defective or worn out, requiring replacement to restore normal operation.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as working with gas appliances can be dangerous. Attempting to fix electrical or gas components without proper training can lead to serious safety risks.
Estimated Repair Cost (2026 UK Prices)
The estimated cost for repairing the F81 fault, including parts and labour, is approximately £150 to £200. This includes the replacement of the flow switch and any necessary cleaning to remove blockages.