My high efficiency heat/ac  unit is at one end of my attic which is unfinished space.  The condensate line which is 3/4 cpvc runs the length of my house (50 feet) in the attic along the soffit.  It then heads down the inside of the outside wall which is insulated and drains into the sump basin which is at that end of the house in the basement.  Periodically when the temps in the winter drop significantly below freezing this drain line freezes somewhere.  I’m guessing it’s in the long run along the soffit.  I’d like to make one more attempt this winter at solving this issue before I abandon the line and figure something else out.  Any suggestions? Last winter I wrapped the line with foam insulation but that didn’t do it.   Anybody have any experience with a heat tape product for drain lines?