How come DX systems don't have to be grouted?

Where did you get that idea? DX boreholes absolutely need to be grouted.

PJC57,

Maybe you are thinking about horizontal DX systems not being grouted.  All wells, regardless for what they are use for, should be grouted to protect the underlying aquifier.

Hi Guys,

This is where I got the idea.
http://www.copper.org/applications/plumbing/heatpump/geothermal/cs_stdy_pa1.html
I believe they just backfilled it with sand and water.

When there is no aquifer involved, it may be legal to backfill with sand and water. This will result (when done properly) in a perfectly functional DX well. However, it's still a better idea to grout the hole with a thermally enhanced grout. Mostly, it's a legality issue with aquifers, though.

PJC57,

Thanks for the reference to the web site about the DX system.  The fourteen holes 50' long drilled at a 30 degree angle is actually only 25' deep.  In most areas, this would be considered a shallow well.

Alton,

I believe that the 30 degrees is off the vertical, putting the depth at about 43' deep.

Yes, it's off the vertical.

Thanks.  Off the vertical would make a difference.