BoilerFaultCodesYour boiler has detected an issue with how quickly hot water is moving through the system, which may result in inconsistent water temperatures.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: DHW flow rate: Hot water flow rate
What causes this fault?
This fault occurs when the boiler's internal sensors detect an unusual or inconsistent flow of water when you turn on a hot tap. It is usually caused by a physical blockage in the flow turbine, a build-up of limescale within the heat exchanger, or a communication error between the electronic sensor boards.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like A-b2 — no call-out fees, no surprises.
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