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Old 03-04-15, 06:40 AM   #5
Mikesolar
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I remember one particularly bad year back in 93 (I think) when the weather was cold enough that the water lines 7ft down were freezing. That is rare but I don't remember ever hearing of building footings having an issue at 4ft. I would guess that you would have stable temps from 10' down or at least no possibility of freezing. Thing is, you have 500ft of tubing in one hole so the 10ft or so at the top won't affect the output much.

That number will be different in the far north tho. The number may be 20ft.
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