BoilerFaultCodesYour boiler has sensed that the water is not moving through the system fast enough, causing it to heat up too quickly and shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Difference between flow and return temperatures too high – check circulation.
What causes this fault?
This fault occurs when the water inside your boiler heats up too rapidly because it isn't moving through the pipes quickly enough to carry the heat away. The most common reasons are a failing water pump, a buildup of sludge blocking the internal pipework, or air trapped within the system preventing proper flow.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after being idle all summer, which can cause internal pump components to seize.
DIY fix possible
Check that your radiator valves are open, particularly any with thermostatic heads.Ensure the boiler pressure gauge is between 1 and 1.5 bar, topping up if necessary.Listen for air in the system and bleed your radiators to remove any trapped pockets.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like E30 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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