40 Emergency
Your boiler has too much water in the system, causing the pressure to rise above a safe operating level.
Technical description: High system water pressure
Typical repair cost: £0-120 (including labour)
DIY fix possible
Check that the filling loop valves are tightly closed.Locate a radiator and use a bleed key to release water into a container until the pressure gauge returns to between 1 and 1.5 bar.Restart the boiler once the pressure is stabilised.
Protect yourself from future repair bills
A boiler cover plan would cover faults like 40 — no call-out fees, no surprises.
*Affiliate links — we may earn a commission at no extra cost to you. Prices shown are starting prices.
Parts commonly replaced
- Filling loop valve
- Pressure relief valve (PRV)
- Expansion vessel
*Affiliate links — we may earn a commission at no extra cost to you.