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
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.
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.
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
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.
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.
>> 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
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...
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.
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.
On Tue, 08 Jan 2008 21:02:41 +0000 someone who may be jill
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.
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
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,