Changing out shower drain
Hello. I am struggling with the shower drain. I am putting in a tiled shower with pre-slope shower bed. It was originally a shower tub so the shower drain is setup for 1.5" pipe. Is it necessary to change it out for 2"? Can you just use an adaptor? I am struggling to figure out how to change it to 2" based on the current setup. I took picture to try and help explain the current setup. I plan on keeping the drain where it is at the end of the shower floor. I do not know where to start with being able to run 2". As you see, the pvc threads to a cast iron fitting on copper pipe. The vertical pipe is the vent pipe that goes up and out of the house. The part you see where it diagonals down leads to the toilet pipe. Any helps is much appreciated.
That all makes sense. But how do I connect the 1.5” pipe to the shower drain? I thought all of the drains are 2”?