BoilerFaultCodesYour boiler is temporarily pausing because it has detected that water is returning to the unit too quickly or at an unexpected temperature.
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: Water pump return water
What causes this fault?
This occurs when the boiler detects that the water returning from your radiators is too hot, suggesting the heat isn't being transferred into your rooms efficiently. The most common reason is that the water is circulating too quickly through a bypass valve or across a small number of open radiators. It can also happen if your radiator valves are all shut or if there is a minor restriction in the pipework.
This code is more frequent in autumn or spring when only a few radiators are turned on, causing the system to struggle with dissipating the boiler's minimum heat output.
DIY fix possible
Check that all radiator valves (TRVs) are fully openEnsure at least one radiator without a thermostatic valve is turned on fullyCheck that the central heating system pressure is between 1.0 and 1.5 bar on the display
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A boiler cover plan would cover faults like S.7 — no call-out fees, no surprises.
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