The water should certainly be heated to at least 50C as a minimum, and this is probably borderline. This temperature tends to excite the H&S brigade as in a shower is would be borderline dangerous, and certainly quite a shock, but that is what the thermostatic controls are for (they work beautifully in my house where the hot water is 90C for the kitchen...). In a large centrally heated (Gas!) hot water system with storage tanks a low temperature is very unsafe as bacteria can easily get in somehow, probably from cold storage tanks. at 37C or whatever they multiply very rapidly indeed. In homes it is much less likely but still 60C is effective to kill bacteria, and probably should be the minimum. Combi-boiler sources and electric showers should not get this problem.
Well designed systems can get the best of all worlds and switch to a higher set temperature to do a sterilizing run for a few hours a week, at a time when it is not a problem, and then save energy from leaking away by idling at something cooler for the rest of the time. For an installation of any size where it really matters, care home, hospitals etc it will have been carefully thought about, and such arrangements, as well as hot water circulating pumps and loops to keep the pipes hot to the taps, and minimize waste while running water waiting for it to run warm.
I'm sure there are plenty of buildings, especially adapted ones, where it is not right, but the problems are well understood, and have been for a good few decades. Mike.
