I'm noting that some of you guys/gals use poly pipe for your systems. In our area hard pipe is pretty much used exclusively. 1. What are the advantages/disadvantages of poly? 2. I'm assuming that most (if not all) of it is installed by plowing? /pulling? (I'll relate a poly story of when the city used it on a project.) 3. What's the largest size poly you use? Is there a diameter that you switch over to PVC or is it "all poly, all the time?"