[tialaramex]

Also you should always store hot water at a very hot temperature (Nasty bacteria thrive in warm water so you mustn't store it) but you should always mix it (with fresh cold water) to a lower temperature for bathing and washing.

So whether it's a tank of 80°C water or a tank of 65°C water make no difference to the 38°C water coming out of the thermostatic mixer in your shower.

[beachy]

You don't need to keep the water at a high temperature all the time.

I don't have the regulations to hand but it's enough to bring it to a high temperature once every few days for some period of time (to kill the bacteria that cause legionnaires disease).