BoilerFaultCodesYour boiler has stopped working because it cannot correctly detect the water pressure in the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Water pressure sensor fault/not connected
What causes this fault?
This fault occurs when the boiler's internal computer loses communication with the sensor that monitors water levels. The most common reason is that the sensor has either developed an internal electrical failure or has become blocked by debris and sludge within the system. Without an accurate pressure reading, the boiler shuts down as a safety precaution to prevent it from firing while dry.
DIY fix possible
Check the pressure gauge on the front of the boiler; if it is below 1.0 bar, use the filling loop to top it up to 1.5 bar.Restart the boiler by turning the power off and back on to see if the error clears.Ensure there are no visible leaks under the boiler or from your radiators.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like F9 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Glow-worm Xtramax is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.