BoilerFaultCodesTechnical description
Water pump return water
What causes this fault?
This fault occurs when the boiler detects water flowing backwards through the internal system or senses an unusual pressure change when the pump starts. The most common reason is a blockage in the pipework or a failing non-return valve that is stuck open, allowing water to move in the wrong direction. It can also be triggered if the pump itself is struggling to circulate water effectively through the heat exchanger.
This issue often surfaces in autumn when the heating is turned on for the first time after summer, as internal valves can seize up during long periods of inactivity.
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.
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