I have 8" double walled stainless insulated Supervent flue on my Kozy Heat 231zc Fireplace. When I was cleaning the flue and replacing a couple fire bricks. I found a split at the bottom section of the flue. I can get to it from the outside of the house by removing one wall of the chase. So that will not be to bad. I built the house 14 years ago so I am going to replace all the pipe while I am in there. Who make the best Pipe? Thanks Dave