have busted cast iron drainage (services kitchen sink, dishwasher and bar sink. Have located area that is broken in wall behind bar sink but and not able to remove/replace pipe myself as the break is in the area that immediately goes under slab/foundation of house. Anyone have ANY suggestions?
As others have suggested, it might be a good time to call a pro, but if you are going to handle it yourself, here is what you should do:
see if you have enough space above the slab to fit a rubber collar of the cast iron/pvc adapter. If this is the case, you should secure the cast iron pipe and cut it. Replace the section with PVC and put rubber adapters on both sides.
If you are not lucky and you don't have enough room, you have to break the slab (usually 4" max) and get to the sand/gravel layer. The main stack should make a 90 degree turn. You should place your cast iron to PVC adapter there. It is just as much work as it sounds like, but it can be done.
Slabs suck. Maybe maybe if there is 2 or more inches of "good pipe" you can fit a rubber collar and a new cast iron pipe cut short. But more likely you're looking at a professional job.
You'll want to understand why it broke. Age of your home would be good to know: is this just the first of many?