Sewer drain replacement

[soparklion11]

I had an issue with my basement sewer piping under my slab basement and now I'm replacing part of it... as I am familiar, anything buried needs to be 4" SCH40-PVC or ABS. The down-drain leading from a bathroom to the 4" pipe is 3" cast iron pipe. Currently, the 3" cast iron meets a Fernco sleeve about a foot off of the floor. I was going to just cut off the rest of the 3" pipe and replace it with a 3 to 4" fernco reducer to PVC.

1. Is there an advantage to removing the old vertical cast iron, or should I just leave it alone?
2. If I replace it, should I use 3" or 4" pipe?

I'm cutting a trough about 1 x 10 ft through the basement slab. Any advice on that would be appreciated.

 

[oldognewtrick]

I'm fixing to do the exact same thing soon.

 

[soparklion11]

I'm fixing to do the exact same thing soon.

I'll leave an update...

 

[Jim greengo]

Picture of the problem?

 

[soparklion11]

Picture of the problem?

Current status on new post, any opinion greatly appreciated:
https://www.houserepairtalk.com/threads/does-my-vent-stack-wye-off-of-the-drain-under-my-slab.30815/

 

[billshack]

cast iron pipe especially on toilets is very silent. i fact some developer insist on all toilet lines be done in cast iron. some building that i have been in when someone flushes the toilet every knows .