Disconnect and remove ABS piping in crawl area off basement and cap just before piping drops and goes vertical. Install new pvc from kitchen across crawl through block wall into unfinished basement. Extend along stud wall towards staircase. Then turn and drop down to tie into 4” ABS stack. This will bypass cast iron running under basement slab. Installation: We rerouted the kitchen drain from the kitchen through the basement to a drop into the slab. For the tankless, we sleeved the T&P line and replaced it with 3/4 copper. Properly terminated both T&P and condensation line out side and sealed. Popped intake outside and properly sealed. Upsized the gas line to 3/4 from 1/2 inch. We installed a crossover tee under the kitchen sink and set Navien tankless settings accordingly.