If you go to a street project where water mains are being replaced, you can sometimes find HDPE water main scraps in the dumpster, and by scraps I mean 10-12 foot sections (a full length of pipe is like 40'). Slides better than PVC, and quite heavy duty.
Sewer pipes are PVC, and 10-12" diameter. These also work well.
inb4 ns collecively shits their pants then rushes into a back alley to furiously masturbate into a dumpster. -PJS.