I’m about to install a mini split AC unit, and attached to the blower is a 2-foot hose for the condensation to drain.  Since my unit will hang on an interior wall, I need to add onto it (the drain line) and run it another 10 feet to the exterior wall where I can punch a hole and let it drip out.  But I don’t know what sort of pipe or tubing to use for the additional run.  The hose that comes with the unit is unique; it’s clearly got some insulation in it because it feels spongy.  It has an inside diameter of 5/8″.  I’ve looked over all the hoses and tubes at home depot and there’s nothing similar.  Then I went over to the electric dept and looked at that gray conduit.  I need something that can stand a lot of heat because it has to run through an attic where it will be quite hot.  Does that gray condiut stand heat?  If anyone has other suggestions, do tell.