Hot water is lukewarm — not hot enough
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Most likely cause & what to check
Run the hot tap for 60 seconds and test the temperature. UK hot water from the tap should reach at least 50°C at the outlet. Below this suggests a setting or component problem.
If you have a hot water cylinder (airing cupboard): find the cylinder thermostat — a small dial strapped to the side of the cylinder. It should be set to 60°C. This is the minimum required under L8 Legionella guidance. Turn it up and wait 45–60 minutes.
If you have a combi boiler: look for the domestic hot water (DHW) temperature dial on the front panel — it is usually separate from the heating dial. Turn it up to between 50–60°C.
On a combi boiler, very low flow rate (partly opened tap) can also cause lukewarm water because the flow sensor triggers slowly. Try opening the tap fully.
If neither adjustment works, the hot water heat exchanger inside the combi boiler may be scaling up — particularly in hard water areas. A Gas Safe engineer can descale or replace it.
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