BoilerFaultCodesTechnical description
Water pressure switch not closed / low system pressure
What causes this fault?
This fault occurs when the internal sensor detects that the water pressure has dropped below the minimum level required for the boiler to operate. The most common reason is a small leak somewhere in your radiator system or air being released through a valve, which reduces the overall volume of water. Without enough water pressure, the boiler shuts down to prevent the heat exchanger from overheating or becoming damaged.
This code is often seen in autumn when the heating is turned on for the first time after summer, as pipes and radiators expand and contract, potentially highlighting small leaks or trapped air.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.