1 in Schedule 40 PVC piston

This is my test piston I made for a 1" schedule 40 PVC pipe. I cut and spliced (2) 3/16" O rings (cut length 70mm) for this, and it threads onto 1/4-20 threaded rod. I tested this, putting it in a pipe with about 10" of water over it and left it for about 24 hours, no leakage, so I'm decently pleased with it so far. With a little oil, it takes about 2 pounds to move the piston. I hope this could take shop air (120 psi), I think it could.

See http://www.thingiverse.com/thing:717976 for O R