OK, before anyone thinks this is a good idea to copy, I need to set some stuff straight here.

PVC is one of the last material your extraction tube should be made out of. Here's a helpful website-
Chemical Compatibility Database from Cole-Parmer

As u can see on this link, with PVC as the Material and Butane as the Chemical. U can see the chemical compatibility of the two. They come out as-
C1-Fair
And that means
Fair -- Moderate Effect, not recommended for continuous use. Softening, loss of strength, swelling may occur.
Look at stainless steel with butane, it comes out as-
A2-Excellent
Its much easier to buy a stainless steel tube at lowes, then worry about the loss of strength or the stripping of plastic out of your PVC extraction tube. Much, much safer!!!

Stainless Steel or Glass
Hope this helps
L8
MJ