When I saw pipe waste first thing came to mind was cast iron sewer pipes. Scrap iron fits far better. I like keeping scraps they do come in handy when welding and fabricating.
WOW! I am just now getting into welding. I have some of the cool tools you have. I have a wood lathe and a floor standing drill press. Wish I had a metal lathe. Just got a MIG, TIG, STICK welder. Hoping to get into making some yard art that moves in the wind. Loved your video.