By cutting in a cast iron Wye so the flow enters the sewer line (soil pipe) at a right angle
If it is "rusted out" you do not repair it, You do replace it with XHCI
galvanized water lines, cast iron drain lines, sometimes lead pipes, terracotta or clay pipes, and in rare cases wooden pipes.
3/4 inch would be too small for anything but just liquids. As long as there is a trap under the sink, there shouldn't be a health hazzard. You will have to be a little creative in connecting the sink drain to 3/4 but possible.
Iron rusts easily when combined with water, and drain pipes have water flowing through them. If iron was used, the pipes would rust within a few days.
The one going out of the wall or floor goes to the septic. The one going up is the vent that should go out the roof.
With a compression mission ring
Yes, it is done all the time
This can be a complicated job as the toilet drain ranges from 3" -4" and a variety of materials from Plastic to cast iron to galvanized. Then there is the venting to consider and NO a shower drain CANNOT be used for a toilet discharge as the shower drain is normally 2" diameter
Downstairs? First floor with a basement or in the basement? If first floor with access in the basement or crawlspace, no real problem. PVC, just cut the pipe and install a T. Cast iron, you can use a Saddle Clamp made for this. Looks like a PVC T split length wise and held to the cast iron with two U bolts. If adding a bath in the basement, you will have to bust out the floor, add the drain and replace the cement.
The shower may be leaking from: 1) A failure of the drain and associated piping itself (e.g., corrosion of the cast iron floor drain), 2) A failure of the shower pan, which is an ostensibly waterproof liner (may be metal or synthetic polymer) embedded in the tile floor (or comprising the plastic floor) which is mechanically connected to the drain; or 3) Leakage of water in the shower's surrounding area (walls, non-pan floor area, etc.) which is accumulating and dripping near the drain.
No less then $6,400 plus tax plus filing fee and inspection fee's patching and back filling is normally an extra
Where? What is your question?
yes.
from the hub to the spigot
Absolutely NOT as the drainage in CI piping has to enter at a 11/14 ,22.5 , 45 deg, 60 Deg as allowing a pipe to go straight in will erode the CI wall
Galvanized pipe for water and drain lines. Cast iron pipe for main drain lines.
Yes, but PVC creates problems