Medium
F40 on Ferroli Domi Compact

Your boiler has detected that the water pressure inside the system is currently higher than the recommended safety limit.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Water pressure too high

DIY fix possible

Locate a radiator in your home with a bleed valveOpen the bleed valve slowly using a radiator key to let air and water escape into a containerClose the valve once the internal pressure gauge on your boiler drops to the green zone (typically 1.0 to 1.5 bar)

Find a Gas Safe engineer
Search the official register →

Related fault codes

F37View →

Related guides you might find useful

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Low pressure — repressurise guide

Step-by-step using the filling loop.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →