Robert Gammon wrote
Rod Speed wrote
Robert Gammon wrote
Rod Speed wrote
Robert Gammon wrote
wrote:

We collect all the shower water in a tank, with an infinite cold
water tank next to it, then circulate the cold water through a
coil in the shower tank until it all cools to the cold water
temp... Then again, infinite tanks are hard to come by.

So maybe mix hot and cold fresh water to 90 F and circulate that
through the coil until the shower tank drops from 100 to 95, then
pump some of the 95 F fresh water back into the hot water tank
and add enough
cold fresh water to make the fresh mix 85, then circulate for a
while, then pump some 90 F fresh water back into the hot water
tank and add enough cold water to make the fresh mix 80, and so
on. How can we do this automatically, on a continuous basis? We
need a 20 gallon expansion tank too. Lots of pumping, but little
energy, if the hot and cold supplies stay pressurized.

At some point the water needs to be heated to about 140F to kill
bacteria before use in showers and baths.

No it doesnt.

Do a little research and you will find that Canada HAS such a spec.

More fool canada. You cant ignore chlorination.

Not Canada, Australia has the spec

http://www.dux.com.au/tech_domestictemp.htm

Read this page, it describes EXACTLY what happened to me at 4 years of
age, why hot water heaters have this spec and why tempering valves can
be a valuable addition to homes with either very your children or the
elderly.

Irrelevant to what is being discussed, whether water
MUST be heated to over 140F to kill bacteria. That
clearly isnt necessary if the water is chlorinated town
supply and the water isnt stored on site before use.

We dont bother to heat the cold water to over
140F before using it in the kitchen, for a reason.