i would like to use a aosmith duraclad oil hot water heater to heat my
pool.

i am concerned that the iron in it will be acquired by the plaster in
the pool and will stain the walls. perhaps the water heater has glass
liner, but won't the heat exchanger contain iron ?

alternatively, perhaps i can open it, add a stainless or aluminum heat
exchanger and close it back up (with a torch). i can get the
exchanger free from a friend steamfitter, but need to rent the labor
with a torch. runtime pressure is 7-15lbs.

any advice ? i got the water heater free (as in free beer) from
craigslist. it will be a great project, if i can get a little
practical advice.

135,000BTU from 1ga and 30,000 ga. from 42F to 75F will cost about
$120-150. That's good for buying 3 months early usage...along with
the bubble wrap i already have to keep down the evaporation. this
equates to $1/day of warmth usage; less inefficiency.