New flange needed; going from tile to vinyl

[casm]

Previous owner for the last 30 years had a slow and steady leak for the last few years. I'm opting to remove the damaged sub-floor and I need help with the flange. The water damage isn't from the flange; I believe it was from the rusty tank bolts. The ID seems to be 4", and the shoulder on the OD leads me to believe it's replaceable.
Is there something that is holding the flange to the pipe besides gravity? Do I need to loosen anything? Should I "'Hacksaw' Jim Dugan" the up pipe below the flange?
My main objective is to put a flange on that will lay flush with the new vinyl tiles I'll install. New sub-floor (OSB is best, right?) then about 3/4" buildup (Ply?) for the vinyl to be level with the existing hardwood floor. Should the flange be level with the flooring? Or slightly recessed? Not sure I want the full weight of the toilet bearing down on the wax ring. Does it depend on the dimensions of the toilet to be used?
Any input from you wise plumbers will be appreciated and used to make the best decision!
Cam

[jadnashua]

It sure looks like a cast iron flange and drain pipe. These are typically bonded together with poured liquid lead onto a packed oakum seal. Several ways to remove it. One way is to drill holes in the lead, pry it out, then pull the old flange off. Another is to whack it with a hammer and chisel to break it (best left to someone who has done it before!). Then, the best thing is to pour a new CI flange, but there are other choices.

[casm]

Thanks for the response Jim. I'll check out some YouTube videos on oakum sealed CI pipe after work, as they are blocked here. That will be a huge help!
One other note: this will still require a 10" rough-in toilet, so I should use a closet bend to get it to the standard 12". Are there any considerations to make the closet bend work here, like cutting the pipe 4" lower (based on the overall height of the floor) or anything that a resilient DIYer could do?

[Gary Swart]

Couple of quick ideas. I'm not a fan of OSB where there is any chance of water reaching it. I'd opt for exterior plywood. I don't quite follow how your idea of changing the rough-in from 10" to 12" with a closet bend, but more directly, working with CI can be an overwhelming DIY job. Not impossible, but it might be worth considering having this professionally done. There are ways to adapt PVC or ABS to cast iron which would be another route to go, but this still would require cutting the cast iron. I am assuming you are going with a new toilet. If so, changing to a 12" rough-in would be a wise decision. Finding a 10" toilet, while not impossible at all, does limit choices. Toto does make some toilets that by using a special adapter that will fit 10", 12", or 14" rough-in, but these models are a bit more costly than other models, and since the 12" adapter is the only one that is standard, you would also have to purchase the 10" adapter. So, since a new flange and some plumbing work is required anyway, redoing the flange to 12" makes good sense.

[jadnashua]

Can't see exactly which way the pipe runs beneath and whether there is a joist in the way or not, but if you can move it to 12" (remember, this is from the FINISHED wall (not including baseboard unless it is very high)), you'll be better off. If you have the room, the easiest may be to cut off the pipe behind the current bend, then adapt to plastic (either pvc or abs, whichever is more readily available where you live). This is something you might be able to do yourself. IF the CI is in good shape, the easiest way to cut it is to actually snap it with a soil pipe cutter. This is a tool you can rent. Unless the CI shatters, it'll take all of about 5-minutes to do it, with part of that figuring out how the thing works! Otherwise, there are saws that can cut it, or you could use a grinder with a cutoff wheel, but that takes a lot more room, and sometimes multiple saw blades. With a 4" pipe, you can tile up to the edge, and use an internal mount flange...otherwise, you need to leave room for the flange to fit over the outside, so you can't run your subfloor or tile up tights. And, if you do leave room around, even with a 3 or 4" pipe, with the right flange, you can leave the pipe long and slide the new flange over it tight to the new finished floor...if you get one with a socket, you have to trim it to the proper height before you can mount the flange, and that can be more of a pain.