As background, I have a 1926 Bungalow that has a cast iron main line and cast iron stack. I had a drain cleaner out a few weeks ago to clean the main line both underneath the house and to the street. One of the clean outs (interior) is at the base of the stack in the basement. When he opened it up, he pointed out an unusual hole that looked like it had been drilled through the stack at the base (I've included pictures here). I don't have a trained eye, but, to me, it looks intentional. Is this at all normal? Should I repair it? I was thinking I don't want holes in my plumbing and that I could maybe get some sort of epoxy to cover it...but I've never done this kind of repair before, so I don't know if there is a better way or the procedure for this. I wouldn't be keen on replacing the whole thing. Any expertise or suggestions appreciated.