This is really just a matter of geometry (trigonometry). If you have a 45 degree isosoceles triangle, the “offset” between the two parallel pipe runs is “x.” You have an isoceleles right triangle with two sides equal to “x” and the calculated run of pipe is the hypoteneuse, “h.” By the Pythagorean theorem, h squared equals squared plus squared (=2x squared). Therefore h=x times the square root of 2. The square root of two = 1.412136 (more or less). That’s how you get the answer. Hope this helps….