[AT] Shop LP Plumbing

[Len Rugen]

I want to run a LP  line in the wall to my future bathroom in the shop.  We used to use copper tubing for this, but with the price of copper, is there another alternative?  I think they run natural gas in black pipe, but I don't have a threading tool, so I'd have to work out exact parts & lengths.  Plastic????  
 
I plan on putting a small unvented "blue flame" heater in the bathroom and probably a larger one in the attached green house.  I don't want the heat to keep the pipes from freezing to be dependent on electricity.  
 
Thanks
 
Len Rugen