I have spent my career working on 50 to 130 year old buildings and found that the original cast iron hold up remarkably well, as long as it hasn't been messed with. Horizontal lines that are not properly sloped do rot on the bottom side. An old hub-and-spigot system like you show can be repaired with the old lead and oakum tools.
Ya this was a large rusty vertical seam crack in the main wet vent only the bathroom sink above it. I think the line may have been plugged up to the crack but not sure. I agree usually only see seam cracks on verticals.
I have spent my career working on 50 to 130 year old buildings and found that the original cast iron hold up remarkably well, as long as it hasn't been messed with. Horizontal lines that are not properly sloped do rot on the bottom side. An old hub-and-spigot system like you show can be repaired with the old lead and oakum tools.
Ya this was a large rusty vertical seam crack in the main wet vent only the bathroom sink above it. I think the line may have been plugged up to the crack but not sure. I agree usually only see seam cracks on verticals.