I'm investigating geothermal for use in an area of South Texas hill country (all rock and expensive to drill in). I have no surface water, and my well is very deep (850 ft) so I use a 2500 gallon fresh water holding tank to ease the burden of the solar powered well pump. I am wondering if I could use this fresh water or even rainwater collection tanks as a sort of closed loop SCW or pond loop exchange. The tanks are concrete and keep the water cool, but more importantly, any heat transferred to the water will be displaced when I turn on a faucet resulting in cool water being brought up from the depths of the earth. This seems logical to me, so I'm a little surprised that this is not mentioned anywhere. Am I missing something? Why wouldn't this work? Does anyone know of this being done anywhere?