Your first thought when needing to cut PVC pipe would be to find the sharpest blade. Remarkably, though, a blade isn't the only tool you can use to cut through PVC piping.
Tie metal rings onto both ends of the cotton string.
Wrap the cotton string halfway around your PVC pipe, and teeter-totter the ends back and forth in a sawing motion. The friction of the cotton string against the PVC pipe will cut right through it.
You can also loop a piece of butcher's twine, or kite string, all the way around the PVC pipe. It's best to tie rings or sticks on the ends as handles.
Pull the string back and forth like a seesaw. This motion will melt right through the PVC pipe.