If your going to do a DIY geo tubing install, where would you buy the tubing? 

Also what diameter do people typically use?

Where do you live? You are looking for HDPE pipe. http://www.isco-pipe.com/ is where we buy ours.
Typical sizes are 3/4" and 1"

a few things to consider:

HDPE joints need to be fused with special equipment
If you have multiple circuits, they need to header into a "reverse return " manifold to insure equal flow to each circuit.
After the ground loop is built, you will need a high volume, high pressure pump to purge all of the air out of the system.
The loop circulating pump needs to be sized for the loop so that you get 3 gpm flow.

good luck with  your project

I live in Portland OR.

 

Is it the same as uponor wirsbo crosslinked polyeth?   I have the tool that expands the wirsbo so that you can plug a plastic or brass fitting into it. You also need a little ring when using the wirsbo. The tool I have will do 1/4 1/2 3/4 and 1 inch diameters..


How do you order the pipe from http://www.isco-pipe.com/? do they have a page to order or do you need to call for a quote?

-Jeff

crosslinked poly is known as PEX which is not the same as HDPE pipe.  With pex, you crimp the joints.  With HDPE, you fuse the joints.   See here

ISCO pipe has an phone number :   Please call 1-800-345-ISCO, send us an e-mail at [email protected], or contact the office below.


If you are determined to do this your self,  you should check out this site.

I am not recommending that you do this,  just making you aware of the option.