Nate Nagel wrote:

Forgot to mention my other idea:

1) buy new 40-gallon electric water heater appx. the same size as
solar one (which is obviously just a modified electric anyway)

2) remove shell from old one, save copper coil wrapped around tank,
discard rest

3) disassemble new tank, slip coil over tank, reinstall shell, fill
space between with lots of Great Stuff(tm) (or just stuff old
fiberglass back in there) Laugh maniacally at having just spent
$400+ on something and immediately voided the warranty.

4) install my "new" indirect solar tank

what do you think the odds are that a brand new Rheem 40 gal. tank
(the internal tank, that is) is the exact same size as a 20 year old
one?
seems a lot of mucking about for not much benefit, still...


You could also just use a regular tank, and add an exterior heat exchanger with
piping between the top and the bottom of the tank for convection flow.