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Old 07-05-18, 11:02 PM   #8
phreich
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Join Date: Jul 2014
Location: Milwaukie, OR
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If you using 1 inch black pipe, then i believe it is made of steel -- not cast iron. It will likely have better heat transfer than cast iron too, because its crystalline structure will likely be much more orderly. Interesting idea of putting a smaller diameter pipe down inside the larger one as the supply, and using the remaining area in the larger pipe as the return.

Since the only real differences between black pipe and galvanized is that black pipe is painted black and galvanized is, well, galvanized, i wonder if it might be better to use galvanized pipe because the galvanization would help slow down the rusting of the pipe. The cost difference isn't that much, if i recall correctly.

I am thinking that another possible option would be to possibly put in a larger diameter steel pipe, and then insert a close fitting thin-walled plastic pipe as a non-rusting inner "sleeve", and then make the smaller "supply" pipe non-rustable -- either plastic or copper. I wouldn't be surprised to discover that there is already some sort of plastic sleeved or inside coated steel pipe manufactured already to deal with corrosive chemicals that might be useable for this.

One of these days I am hoping to leverage off of everyone's experience on this forum and do my own closed loop vertical pipe ground source heat pump.

Thanks for sharing your ideas and experiences everyone!

Philip
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