Steve wrote:

Good question! One of the thermostats went out on my old heater. It
was 30 + years old and I figured it was as good of a time as any to
try this tempering tank idea which I have been thinking of trying for
a long time. It just might be a dissapointment but I am willing to
try it.

I didn't read all the details in the original message, but have you considered
the total energy flows?

If the tempering tank is inside the building thermal envelope, the energy needed
to bring the water up to room temperature has to come from somewhere - most
likely your space heater. So, it isn't free.

If the tempering tank is outdoors, you have to consider that you have an
unheated space that will be chilling the water for at least part of the year...