I recently leased a warehouse space in which I am trying to add a shower to a current half bath. There is a mini basement right below the bathroom which contains the plumbing.
Attached is a photo of what seems to be a series of drains from other fixtures coming into what I assume is a sewer ejector pump before it makes its way out of the building. My question, assuming all of this so far is correct, is whether I can add in another wye fitting into this main stack for my shower drain.
For reference my shower will be right above my head where I took this photo so about 2-4 feet max. One follow up question is if there is any opposition to the new drain from the shower to be PVC instead of cast iron. Any help would be much appreciated. Thanks!