Hello, I am an energy efficient home builder who is also looking to expand my company to include geothermal systems. I have been putting together a team of subcontractors for the ductwork, system install and well drilling required for the systems I plan to install on the new homes that I build. I have been interested in questioning some of the "rules of thumb" that most geo installers in my area abide by. In eastern CT everyone seems to like installing vertical bore systems with 1.25" diameter pipe, however, I have had several conversations with engineers and sales people of some of the big heat pump manufactures and they all seem to reccomend .75" or 1" pipe. My understanding is that 1.25" pipe doesn't offer nearly the same thermal conductivity because of the reduced amount of surface area of pipe to loop fluid in a larger diameter pipe. Every installer around here also seems to have their own feelings on the correct number of feet of loop per ton to drill. This leads to my second question: Is 150' per ton of loop sufficient for both .75 or 1.25" piping or is it for one or the other? Lots of conflicting information has passed my way. I would be interested in some professional opinions outside my area. Thanks for any reply.