How to Bend 4" Clear Schedule 80 PVC Pipe

My task was to bend clear schedule 80 (very thick) 4" pvc pipe to be used to demonstrate flow of liquid in a facility. Since I had not bent this pipe before and needed to achieve 15 and 30 degree radius bends I decided to use our method of inserting smaller pieces of flexible metal hose into the pipe and then placing the PVC Bendit in the center and plug the ends with paper. This method helps to heat the pipe more uniformly.  

Video How to bend PVC pipe

We used 4" pvc pipe insulation to help keep the heat in the pipe.

It took about 30 minutes to get the pvc pipe near the correct temperature so it would be soft enough to bend. I then carefully began bending the pipe and found it was not uniformly heated so I rotated the pipe 180 degrees, waited a few minutes and finished the bend.