I called the local supply house, 6"X20' pipe cost $57, fine, that can make 4 tubes, but the caps were going to run $32 for glue on cap, $52 for the pipe plug that screws in and $47 for the glue on piece w/ threads.
What's a cheap way to plug the ends and be removeable?
These are NOT for burial! They will just be stored in a shitty building with leaky roof and potential for flooding.