I have a fake steel chimney that has a 4" galvanized pipe inside. Everything is rotting and rusintg, and staining the roof with rust. I see a few of the houses in the neighborhood that have no leaks and some that are doing the same as mine. It appears that I need to replace this 40+ year old unit with something new. I have not been sucessful in finding such, since I am new to this. Can you help with ideas?