Hi all, I'm building a bathroom and have to tie into cast iron- I have quite a bit of experience with abs, but not CI. The best way to create the new waste run would be to tap into the 4" cleanout you see in the picture, but it's in a hard to access spot, and on initial inspection, it looks like a brass plug that may be soldered in. I can crawl in there Monday for a closer look.. Does anyone recognize this type of plug and does it make sense that a cleanout plug would be leaded in? Or maybe it's threaded with some kind of sealant? Can someone walk me through how to remove this plug and tap in with ABS? Thanks much.