Hi everyone. I'm in the middle of a major remodel to my 1947 home, including adding a second story. We're trying to do everything top-notch, which leads me to the experts here. Here's my question: For the waste/drain pipes, I know we want to use cast iron in the drops between the floors (for sound attenuation, etc.), but should we use cast iron for the horizontal runs as well? In other words, should ALL the waste/drain pipes be cast iron? That's what I was planning to do initially, but then a friend recommended doing the horizontal runs in PVC and the vertical drops in cast iron (something about standing water in the horizontal runs potentially damaging/corroding the cast iron), but I don't like the idea of switching back and forth between cast iron and PVC. What is the "best" way to do it (without regard to cost) -- all cast iron? Thanks!