I'm going to be working on a project soon that uses very, very large
smoothbore plastic pipe. It needs to be 24-27 inches in diameter, smooth on
the inside, and not too incredibly heavy. It'll be under a slight vacuum.
I've been looking at the green PVC sewer pipe, which is supposedly available
in those sizes, but it's not going to be easy to get. Apparently it's not
used a lot for some reason.
It is very important that the inside be smooth and pretty consistent in
diameter.
Does anyone know where I should be looking or if there is anything
better for this application?

Metal content: Remaining components of this project will be made of mild
CR steel, and aluminum, mostly 6061. Wiring most likely made of copper