78 High
Your boiler has stopped working because the water pressure is either too high or too low to operate safely.
Technical description: Water pressure out of range
Typical repair cost: £0-120 (including labour)
DIY fix possible
Check the pressure gauge on the front of the boiler or via the digital display.If the pressure is below 1.0 bar, use the filling loop valves to top it up to 1.5 bar.If the pressure is too high, bleed a radiator to release small amounts of water until the gauge returns to 1.5 bar.Reset the boiler once the pressure is within the correct range.
Protect yourself from future repair bills
A boiler cover plan would cover faults like 78 — no call-out fees, no surprises.
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Parts commonly replaced
- Filling loop
- Expansion vessel
- Pressure sensor
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