F40 Emergency
Your boiler has too much water inside its system, which can put unnecessary stress on the pipes and seals.
Technical description: Water pressure too high
Typical repair cost: £0-120 (including labour)
DIY fix possible
Locate a radiator bleed valve and use a key to slowly release water into a cloth or container.Monitor the pressure gauge on the boiler front until it drops back into the green zone (usually 1.0 to 1.5 bar).Ensure the blue or black filling loop valves under the boiler are tightly closed to prevent more water from entering.
Protect yourself from future repair bills
A boiler cover plan would cover faults like F40 — no call-out fees, no surprises.
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Parts commonly replaced
- Filling loop valve
- Pressure relief valve
- Expansion vessel
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