Durring the summer months does the stream you are planning on gathering deco from have alot of suds, bubbles, foam, soap sud looking things in it near the ripples, current, and stagnant pools? If so I would be leery about using rocks from there. If you do decide to boiling should be a good way to get all pollutants out of the rocks. PVC
is okay. Clear tubing seems to be the choice so you can see what is going on inside. However this takes away from the natural look of your aquarium!