For years I've admired pictures here of nice, straight, rigid PVC work. And I've got this. :-(
It's a mess, right?

Look at the conduit for the pool lights running over the top of the PVC. Other than it looking really wrong, what's the structural problem?

Anybody know what the lone piece of rigid sitting across the T-section is for? And what's the really thin one?

If this pipe is smooth it may not be sch 40 flex pipe. All the info is printed on the pipe. Schedule, Class, PSI rating, Usage. You might gather this info so you are clear what you have. I know they make a smooth wall (class 200 I think) pipe for irrigation that also comes in a roll. This is generally cheaper than 20' lengths of sch. 40 PVC.

It is somewhat flexible because it has a thinner wall than schdule 40 pipe. You will normally see ribs on flex pipe that I described in your original post.

When we were in the early stages of the pool process... our PB showed us a piece of flex pipe, and how termites attacked it, yada, yada, and they stated that they ONLY use rigid... the section of flex pipe he showed us was ribbed.... looks nothing like the pipe in your pictures.

Looks like flex to me. I seriously doubt they heat bent the runs in the last pic. Rigid pipe comes in 10 and 20 foot lenths. If you have a 25 foot straight run without fittings, it's flex.

Scott