I didn't want you to be alone. Our service manager extrodenair was also a drainage engineer when he was in the field. It is hard to tell wire from pipe but the pipe is 3/4" PVC ran over 80' with about eight supports. The pipe is for the split and of course it's overflow pan since it is all over cubicles...ya know you wouldn't want a leak or anything.
It's a wet vent plumbing stack. It is not legal but works. With all that water in the "sag trap" one does not have to worry about it drying up in the winter and sucking in methane gases from the plumbing stack. Is that copper pipe? Would not last long around here.