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Discuss Hot water temp Query in the Water Regulations area at

Good morning everyone,

I would like to know when you run the hot water tap in the bathtub by law/water regulation how hot should the water be set at without mixing any cold water? I used a thermometer today and it came at 45c, should it be higher or is that okay?
I have a combi boiler in the kitchen and it doesn't show you the temperature in numbers but has a dial of 10 dots currently the hot water dial is in the middle (5th dot), any information would be great thank you.


Gas Engineer
Advent Win
45 degrees out of a combi at this time of year is absolutely fine , bordering on excellent.


The UK Water Regulations state that the hot water should reach 50 degrees centigrade at any outlet within 1 minute of opening the outlet.

Edit to add - That's for stored hot water so I think the other folks advice here is correct as you have instantaneous hot water.
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Thank you for the reply and it is a 2nd floor flat in the UK (circa 1960) and I got the combi boiler installed in September this year and a new bathroom in October this year. I just wanted to make sure I have the correct temps set for the hot water so that their are no concerns over the water temps, thank you once again.
@BobbyJoe as above have said, at this time of year with cold mains slightly lower temperature than warmer months 45°C is normal. Remember a combi boiler will increase cold main water to roughly 35°C higher for hot water demand, obviously in the colder months final result will be a bit lower and warmer a bit higher.
If you had a hot water cylinder instead of a combi, then this should be heated to 60°C but this is irrelevant in your case.
Yes as chking said. Reducing the flow rate will produce hotter water. Either crank tap open a little or close incoming main slightly. Remember to reverse in warmer months

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