This dial on my hot water tank what should I set it too?


Hi all.
We have a hot water tank with a dial on the side ranging from 40 degrees to 80 degrees, what would be the best setting for economy as our gas bills are enormous for some reason about 140 a month. We had a Micro Glow-worm 80FF boiler two years ago.
There is also a switch on the wall with a cable running from it to a small black box which has a large copper pipe running through it. I assumed this was an immersion heater and turned it off at the switch. How do I know if it is an immersion heater and should I have switched it off?
Sorry to sound thick but I know nothing about central heating etc.
Any help appreciated.
Thanks
Haymish
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60 degrees
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60C is ok for hot water. If you find the hot runs out when showering you can increase the temp to make it last longer.
But this wont have much effect on your 140 a month, something is very wrong.
NT
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to
are
it
The small black box with a pipe running through it? Sound to me like a booster pump for the shower outlet. Is it near a shower? Or is there a shower fitted over the bath or somewhere?
Does the pipe connect to one side of the black box, and emerge from the other on another connection? Or does the pipe look as though it runs continually through the box?
Have you switch the control box off for the central heating system?
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