In alt.solar.thermal Rod Speed wrote:

What explanation is there for this heat requirement,

Basically storage hot water services can end up with
a significant problem if they arent run at a high enough
temperature to kill bacteria, in situations where the
water supply isnt chlorinated like with wells etc.

which doesn't exist in most other parts of the first world?

It does actually. Most obviously with Legionaire's Disease.

And the use of unchlorinated wells with residential
property is much more common in north america too.

I have lived on well water for many years. Some people treat water drawn
from shallow wells, but I don't know of anyone that does any treatment to
deep wells.

I find recommendations to raise the temperature to 170f to kill hydrogen
sulfide to get rid of a rotten egg smell, but even those sites say it is
harmless.

Most of the advice is to set the temperature to 140 if you have a
dishwasher, 120 otherwise.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5