I am looking to install a basement bathroom. I believe I have 4" Cast Iron waste pipe under the slab. I will need to tie the toilet and shower into the horizontal waste line under the slab. I have been told that the Fernco-type couplings with the metal bands are not acceptable if they are in the ground as they will eventually corrode. Can anyone tell me what product is out there to tie new ABS onto existing cast iron when under ground? If possible, can you post a link to where they can be purchased?