Mark and Cut the Pipe
Mark the pipe, and then cut the pipe using a pipe cutter. It's crucial that the cut is square; therefore, don't use a hacksaw for cutting copper pipe.
Using a pipe cutter is simple. Adjust the wheels so the blades push into the pipe, but be careful not to over tighten or you could pinch the pipe -- bending it out of round. Turn the cutter around the pipe (Image 1), tightening it slightly after every two or three turns. The pipe will eventually come off. The edges of the pipe will be sharp, so be careful.
The same rules of measuring used for copper pipe apply with CPVC. Always leave enough pipe for the fitting to fit snug into the fitting's shoulder (Image 2).
PVC has its own tools for cutting. Note: The cut should be square, or it could create a weak spot in the joint.
A ratchet cutter is one of the best options for cutting PVC. Open up the tool, put it into position, and then squeeze the handle until the blade comes into contact with the pipe (Image 3). Make sure the blade is straight, and then squeeze the handle until the blade goes all the way through.