As explained on the temperature control page, geothermal heating and cooling is used with the outdoor wooden composting bin. This page details the construction of the tubing needed to make this happen.

First, the end result. The black tubes are ABS and the grey are PVC. The black tube sticking up will be the air intake, sticking up out of the ground. The rest of the black tubes will be buried in the ground and the grey tubes will be buried in compost.

1/4" holes were drilled in one side of the grey tubes. These will be facing down in the compost bin. The other side has no holes and will be facing up. This is so that fluid does not fall into these tubes.	Fly netting was then wrapped around the tubes so that the worms don't start crawling into them.
1" diameter holes were drilled into a black tube and grey PVC couplings were inserted into these holes and glued in place using PVS-to-ABS glue.	All the black tubes were assembled and the grey tubes were then placed in the grey couplings.

The grey tubes were then removed from the couplings and placed into the bottom of the composting bin with their ends stick out the lower ventilation holes. (Yes, when I took this picture I did notice that the newspaper on top was dry. :-))

The place where the grey tubes stick out was then covered in silicone caulking to be waterproof.

The whole thing was then put together by inserting the ends of the grey tubes into the grey couplings.

The whole thing in place, ready to be buried in dirt.

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