I would like to smooth out this pipe. I know that I should have made it out of a curve. Is there any way to smooth the pipe?
Indeed it would be easier to deal with this type of geometry using Bezier Curves instead.
Otherwise just use the Bridge Edge Loops operator.
Erase the straight corner faces, select both end edge loops, call the Bridge Edge Loops from the Space bar Menu, then adjust the number of cuts and smoothness as desired.