Here's food for thought:

I intend to divert my return water through a "cooling field". (You gotta' have a lot of room to do this) Once I can find a deal on 700' of 3/4" copper pipe, I'm gonna make a manifold and take my 2" return line into 7 - 100' runs of 3/4" copper. I'll bury those 7 pipes about 6" apart and 4' deep. By the time my return water makes it's journey through the copper and comes back together (joining my regular return lines), I'm hoping my return water temp will be around 80 degrees. The only thing I can't quite get a handle on is how well the surrounding soil will dissipate the heat given off by the copper pipes. If I cannot dissipate the heat quickly enough into the surrounding soil, my returning water temp will not get low enough to effectively lower the temp of the whole pool.

This experiment is waaaay too pricey with new pipe. I've been looking on the net and locally for something surplus....nothing yet...I'll post the results when I find the pipe!!