Totally Tubular

Quick update today. The drilling company installed the tubes and thermal grout in to the 290-foot-deep bore holes. The tubes will hold a water and propylene glycol solution that will be the heat transfer medium for the ground source heat pump. It only took a couple of hours.  You can see in the photo on the right a clever little jig they attached to the casing to help guide the tubes in to the hole.  

The tube is U-shaped and was pressure tested before they inserted it in to the well. On site, I believe they had to fill the tube with water before they could sink it in to the hole.

The big surprise to me was the thermal grout. The thermal grout is supposed to help the tubes make a good thermal connection with the ground. They used a substance called Therm-Ex. It is supposed to remain soft and flexible so that the tubes can expand and contract as they change temperature. Some how I imagined (incorrectly) that it would be more like a rigid cement.

When they pumped in the thermal grout, the water that had accumulated in the hole poured out. Now I realize why the last crew (the drilling crew),  just before they left,  dug a small pit and trenches to that pit. They were planning ahead for the pipe-and-grout crew.  It was impressive forethought based on their experience.  The pit kept the water spillage contained nicely.

Tomorrow the third and final outside crew comes to excavate a trench 4-feet down between the holes and then on to the foundation. They'll bore 2 holes in to the foundation. The two U-pipes will be connected in parallel and the connecting pipes will get inserted in to the basement. They run the pipes 4-feet down to use the ground as insulation for the water in the tubes.