Have a 500' vertical loop located about 100' from home. How far apart should the 'supply' and 'return' pipes be? Two foot (typical trench width)? Or dig two trenches further apart (40' is possible in this application). While it would seem obvious to 'spread' the pipes farther apart to increase ground area involved, at some point there is a practical limit ... after all, the 2 pipes that make the vertical loop are very close together. Any thoughts?