I would try snapping a chalk line. But the chalk may not want to stick. In that case, I would try roughing up the PVC with some sandpaper so there is some tooth for the chalk to stick to.

A regular 10 inch table saw should do the trick no problem, assuming you are proficient with one. I would hot glue stabilizing blocks to the outside to prevent rotation for each pass. With this method you won’t need to bother with drawing lines on the pvc.

Sorry, I should have mentioned that I don’t have a table saw or bandsaw. Power tools are limited to jigsaw, reciprocating saw, or circular saw.

Is this a puzzle? :)

This is most easily done with a handsaw. Using two 2x6s and four 2x4s a foot or two longer than the pipe, and a little scrap lumber, make a simple square jig that holds the pipe and has slots on the top and bottom. This will guide your saw down the center of the pipe's width. (Think of how a miter box works.) Clamp the pipe in the jig, stand the jig on end, and cut through both sides of the pipe at the same time. Be careful not to cut too fast so you don't melt the plastic.

Table saw, please.

Without something like a table saw the cut line is never going to be perfectly straight. If straightness doesn’t matter, you can just use your circular saw with the pipe clamped down and eyeball it.

Looks like you can justify a new table purchase!

Without something like a table saw the cut line is never going to be perfectly straight.

The jig I described cuts straight, and it's a lot cheaper than a table saw. Safer, too, IMO. Build it with screws, and when you're done, you can easily take it apart and use the lumber for another project.

DavdR’s recommendation maybe similar to an Alaskan Chainsaw mill.

Hey DavidR! Nice to see you around. I don’t doubt your method could work assuming square lumber. It just wouldn’t work for someone impatient like me ;)

Yep, making a jig for a task like this, instead of jumping in and freehanding it, takes a little more patience. That comes with age, and I'm getting more of that all the time. Age, I mean. I'm not so sure about the patience part. :(

It's an idea I came up with several years ago, when I was planning to cut some PVC pipe in half to make a mini-split lineset cover. I ended up not having to make the cover after all. But I've used similar jigs for smaller jobs, and I'm pretty sure it will make smooth, even, consistent "troughs."

Impatience will have you wearing PVC.

mike-

The question I have is: How long is the piece of pipe? If I were doing this, I'd want to use the safest efficient technique, and that depends on how long this is.