Domestic Hot Water Temperatures?

Prompted by two threads: the one concerning the child who was burnt
due to faulty immersion heater - and the one I made re recommending a
thermometer (which I have now bought)
What would people recommend for the temperature of water coming out of
hot tap?
I am thinking it wants to be just too hot to put your hands in
(temp??) as otherwise it will not be hot enough to wash dishes etc -
much hotter and you finish up wasting the heat as you add cold water
to cool the hot down.
Views?
Reply to
jill
I think it depends on which tap.
Bath and basin taps are more likely to be used by young children, and can (and I think in Scotland now must) be fitted with thermostatic mixing valves. "just too hot" for adult hands is still hot enough to cause injury to children, especially in baths and showers.
Kitchen tap less likely to be used / reached by young children, hotter water is useful here. Although it's easy enough to top up the washing up water with a boiling kettle if needed.
Owain
Reply to
Owain
Why don't you play with the thermostat until you're happy?
Well firstly that perhaps physics wasn't your favourite subject at school. Subject to the rider below, you aren't "wasting" anything by adding cold water to the hot. You're ending up with the same final volume and temperature of water in the sink or bath and hence the same amount of energy taken to generate it. What you're doing by heating the immersion to a lower temperature is substituting a smaller volume of very hot water plus some cold for a greater volume of hot water at a lower temperature plus less cold water. The energy used doesn't change.
The rider is that the hotter the immersion tank the greater the losses from it but most of those will help heat the house anyway so it's not much of an issue except in the summer. With modern lagging those losses are actually very low.
If the water is only just above hand temperature you'll never be able to top a bath back up to temperature with it if you want a long soak and if you put even a tiny amount too much cold in water in you'll have to drain it and start again. Even with my immersion stat at its max of 60c it's too cold to top a bath up again without either A) filling it to the brim or B) running out of hot water first anyway or C) letting half the water out first and then finding you're back to B) again because the immersion tank hasn't heated back up fully yet.
In fact I've literally just stepped out of a bath which I put a bit too much cold in when I was running it, didn't have enough hot left, or at least enough hot at a high enough relative temperature to top it back up and ended up having a lukewarm bath instead of a nice toasty one. It's a pain in the bloody **** not having the old immersion which used to get the water properly hot. Bloody stupid new government rules are to blame for no apparent purpose as far as I can see. I want my 80c hot water back again but I won't get that until I mend the boiler.
Reply to
Dave Baker
Deopends on who is in the house. Ours is pretty hot - about 70C, and is enough to really hurt, but we are adults,and it means there is a shade more hot water for baths and showers in the fixed size of tank.
We don't have mixer taps either.
IIRC 60C is recommended as a maximum. And with kids maybe 50C.
Reply to
The Natural Philosopher
>
>> Prompted by two threads: the one concerning the child who was burnt >> due to faulty immersion heater - and the one I made re recommending a >> thermometer (which I have now bought) >> >> What would people recommend for the temperature of water coming out of >> hot tap? > >Why don't you play with the thermostat until you're happy?
>Well firstly that perhaps physics wasn't your favourite subject at school. foc
Reply to
jill
On Tue, 08 Jan 2008 22:05:22 +0000, The Natural Philosopher wrote:
Thanks - that was the sort of sensible comment I was hoping for.
Reply to
jill
For what purpose, hand washing, doing the dishes by hand?
That would be my minimum for hand washing dishes but its' rather hot for ordinary hand washing. Dishes I'd want above 60C from the tap, it soon cools in the bowl with all the cold dishes going through.
There is legislation about hot water tap temps. IIRC 43C is the maximum in places with the "vulnerable", hospitals, sheltered accomodation etc for basins/baths/showers. Trouble is there is also legislation about the minimum temp for stored hotwater to stop things growing in it. That minimum is 80C (again IIRC) hence you know find thermostatic mixers under all those fittings...
Reply to
Dave Liquorice
In message , jill writes
Yes, education in the Uk is Free of Charge - your point is?
Reply to
Si
In article ,
I think you'd have problems getting the water in an indirect storage system up to 80C. Think the magic figure for killing most bugs is 60C.
Reply to
Dave Plowman (News)
60C is recommended as a minimum for stored hot water, to prevent bacteria breeding. That is too hot to hold your hand in the water, but will not normally cause injury in the time it takes most people to register the fact and withdraw their hand.
43C is the maximum at which prolonged contact is unlikely to cause injury and should be used if there is anyone who may not have full feeling, might collapse or otherwise might not be able to withdraw from contact with the water. The best way to achieve that (and the only safe way if you have stored hot water) is to use a thermostatic mixer valve to feed the hot tap.
Colin Bignell
Reply to
nightjar
Yup. I reckon thats about it.
In most areas, the water is chlorinated enough anyway for bugs to not be a huge issue.
I must say I thought 50C was infinitely sustainable, but I'll take your word for it.
Reply to
The Natural Philosopher
...
I have to pay a lot of money to get things certified to 43C, to satisfy the NHS.
Colin Bignell
Reply to
nightjar
On Tue, 08 Jan 2008 21:02:41 +0000 someone who may be jill wrote this:-
You need to describe your system.
If you have a storage system without thermostatic mixing valves then water will come out at much the same temperature as it is stored at, when enough water has been run through the pipes. As others have said 60C is the recommended temperature for storage.
If you have the above but with a thermostatic mixing valve then water will come out at the temperature the valve is set at. The storage temperature should be higher than that.
If you have an instant water heating system. Combination boiler, thermal store and various other "instant" heaters water will come out at a temperature determined by heat input and rate of draw off. The lower the flow the higher the temperature. The second sort are likely to be fitted with thermostatic mixing valves.
Reply to
David Hansen
I have recently been trying to get the rooms all at comfortable tempeertatures across the house, ans was really struggling.Upstairs was wat too warm in an evening, and cold in a morning. I was putting it down to convection, and backing off upstairs radiators and starting the heating earlier.
Then I had rather a realisation, It was not *always* too hot upstairs in an evening.
My wife had a habit of using the door from the airing cupboard to hang the washing up, leaving the door wide open, so the cylinder was effectively a very large radiator for upstairs.
The cylinder just had the spray on foam lagging. It now has an extra jacket and a closed door,
P.
Reply to
Paul Matthews

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