Good information. Thanks. I only mentioned a bore hole as an example. It's not what I intend to do. The amount of red tape in this county for a drilling permit is prohibitive for me. It's a very water sensitive area, and the burden of proof that I wasn't drilling wells would be too great, so that approach is not being considered. I took a years worth of temperature samples at the surface, 20", 40" and 60" down in the area where the source pipes will go. I put four sensors in a piece of 3/4" pvc pipe, capped the lower end, filled it with dry sand to keep the sensors in place and give conductivity, put a u-bend on the top to keep water out, and recorded the temperatures every night for a year. The upper sensor varied between 48 and 73. We're close to the Pacific which is a great stabilizer of the local temperature. The lower sensor varied between 55 and 64. The sensor at 40" below the surface varied between 52 and 65. It seems to me that 48" deep wd be just fine for the source pipes. I'm imagining I can dig a narrow slot type trench four or more feet deep and bury the loop with the return portion in the bottom and the out going portion of the loop perhaps 2.5' down with each loop being about 300' long in a 150' trench. At 2' apart, I have room to install ten loops for a total of 3000' of collector pipe for a 2.5 ton heat pump. Perhaps that's far more ground source pipe than I need, but in order to find out, I'm installing one such loop which I'll connect to my small E-Tech heat pump, and monitor the rate at which I can extract heat. It should give me sufficient data in order to design the heat exchanger we need. mm
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