I will be building a new house in 6-12 months and will be going with a closed loop geothermal system for heating and cooling. I live in the Dallas area and have a nice 3 acre pond on the property that is 10-20ft deep in the deeper areas. I will get the exact numbers from a professional, but my current estimate is that I will need a 8-10 ton system. So probably two 4 ton or 5 ton units. My preference would be to lay straight runs of the PE pipe on the bottom of the pond and eventually let sediment cover the lines so that I don't have to worry about getting fishing hooks caught or other potential damage to the lines. It is a private pond and I could do straight runs of pipe up to about 500ft each way (1000ft loop) without any problem. To simplify the system I would like to run one larger size PE line for each geothermal unit (say 800-1000 ft of 1 1/4 inch line). It may be a little more expensive for the 1 1/4 line vs using 3/4, but I think it would eliminate the manifold system, simplify the plumbing, and increase the reliability of the loop. Doing a long straight line would also dissipate heat better than having overlapping slinky or coiled pipe. Has anyone done a system similar to this? Any recommendations on pipe length for 4-5 ton loops? The middle depth pond water in the summer tops off about 80-82 degrees and drops to about 40 in the winter. On the bottom of the pond it is probably a few degrees cooler in the summer and a few degrees warmer in the winter. I've attached a picture of my property and proposed loop lines. Any thoughts?