Virginian, Schedule 40 perhaps?
6" Sched 80 PVC weighs about 6 pounds/ft, the pipe costs about $100/ft and end caps cost over $100 each, and that was >15 years ago.

To all,
Remember - if Hillary wins, there will be a run on 6" pipe and endcaps. Sched 40 holds up very well when buried and supported on all sides.