CaptFish;160717 said:I don't think you want the hard board insulation, it may hold the heat in. I would cover it with good old grass.
Aye, but you do...
We're talking 6' down. Put grass or whatever you want up top. The insulation will keep the plumbing insulated FROM ABOVE, where the temp varies seasonally. Insulation only goes over plumbing, not under.
If you're serious Noah, Best to find a reputable geo-thermal guy (or gal).
A guy up here has 3, 1000g concrete septic tanks buried under his garage. They're accessible, and have stainless heat exchangers in them and are used to aid heating in winter and cooling in summer. (fairly big house) He wanted to do something geothermal, but couldn't afford 3, 300'+ drilled wells (around $20k).
I do not believe "testing" through a sprinkler system will tell you anything. Those are plumbed just below the surface where ambient temp varies. Below 4' or 5' temp should be constant 50 - 55ish. Asking / hiring the engineer is the best advice here yet.