I know pvc pipe structures don't draw as many crappie as wood, but I have been using them for 6 years now and I know they will draw crappie. And once you have them placed and marked with your gps, you never have to worry about having to replace them.

The area of east Texas where I live has lots of plant farms. These industries use lots of 1" scedule 40 pvc in their green houses to hang plants from and drip water from. Every so often they have to replace them and simply have to throw them away. If you have a plant farm nearby, tell the owner what you use the pipe for and promise them a mess of fish and you will probably have access to more pvc than you can use. Good luck.