BoilerFaultCodesYour boiler has a buildup of mineral deposits that is preventing the water from heating up correctly and may cause it to make a loud kettle-like noise.
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: Limescale in heat exchanger
What causes this fault?
This fault occurs when minerals from your household water supply gradually build up inside the metal pipes of the boiler's heat exchanger. Over time, this layer of limescale acts like insulation, preventing the burner from heating the water efficiently and causing the unit to overheat or make loud banging noises. The most common reason is living in a hard water area without a scale reducer installed on the mains inlet.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like C1 — no call-out fees, no surprises.
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