Marshall Brain's Blog

He probably could have done the same thing using some coils of tubing (little soldering) and a bit of ductwork.

My opinion of using propane (actually LPG, derived from petroleum) to heat outdoor swimming pools given the economic and politics of the energy source is another matter entirely.
 

Backyard engineering is going to save society...mark my words.... -B
 

The link to the efficiency calculation is a nice touch. 83% is pretty good.