Question

PVC Piping and degrees using circumference

Answer 1

Sorry I'm a bit confused. So you have a PVC pipe with a circumference of 3.4375 inches and you're going to be burying this pipe downwards, tilted 10 degrees in one direction and 25 degrees in the other? And you're wanting to know how far the pipe should be at its deepest point from where it first entered to know it's at the correct angle?

Answer 2

How long's a piece of string?

If you know the length of pipe we can tell you the horizontal length of the trench/tunnel.  

If you know where your start and end marks are, we can tell you the length of pipe you need to buy.

Unless I'm also confused about what you want, I don't think the width and thickness of the pipe and the pipe wall are relevant.