Install 6" PVC butterfly valves
I want to install 6" PVC butterfly valves in a 6" PVC potable water line. I find three types of butterfly valves: standard, which has a collar, or "lugs," around it with bolt holes through it; lug insert and true lug styles, which have threaded metal lugs in the bolt holes; and a wafer type, which has no collar at all, and which the description says is to be used between two flanges. Aren't all of these valves used between two flanges? Which should I use and why?
Can I use a valve with Buna-N seats, or does code require EPDM for potable water?