I am nearing the end of a large diy new construction home. I am about to put in the driveway and my loopfield. I have a particular design in mind that i came up with from reading posts on here. My units are miami heat pump 2.5 ton and a 3.5 ton. I live in southern louisiana were the water table is very high (about 5'). I have some clay but mostly very well compacted dirt, easy to dig though (I have my own excavator). The 2.5 ton requires 7.5 gpm and the 3.5 ton requires 10.5 gpm. From my research on this it will require about 2550 ln.ft. + 30% for the slinky. Total would be 3315 ln.ft. which i would round up to 3600' of 3/4" hdpp. I only have about 90' (at most) of possible trenchs. If i do 18" pitch with 3' diameter, i would have about 20' of pipe per 3' of trench. So each trench would have around 600'. The design i would like to do is dig down to 9' or 10' (no one would be entering the trench) and lay the first layer of pipe. Backfill to 6' and lay the second layer. The two layers would be one continous flow at 1200' long. 3 trenches = 3600'. I was going to run the six ends into the attic to the flowcenter into a manifold. Each unit has its own pump supplying the manifold. Is this a good way to set up the manifold or should i separate to 2 loop fields? Is this enough pipe to adequately exchange heat for 6 tons? If i do the double layer slinky is it best to supply to the upper layer with the heated fluid and return from the lower or vice versa? Or Should i set up the slinky with the return along the whole 1200' run? In other words enter the top layer slinky run the 90', make the bend to the lower, make the 90', then return the lower 90' on a straight run, make the bend back along the top 90 and back to the unit. This way seems that the heated fluid would effect the upper cooled return, but i don't know. this system was designed by a igshpa accredited designer. It called for 5 tons, but he advised stepping up both units 1/2 ton because the size of the house and amount of windows, so i did. It was also designed with verticle loop field, but the installer disappeared and now i dont have the money to hire someone else. I more than have the capabilities of doing a horizontal field with a little guidance of course. There are very few people down here that knows anything about these systems so i am turning to you guys. Thanks in advance for the help.