There is a PVC drain on the floor of the laundry room. I inserted a 1
1/2" pipe in it but the hole is slightly larger. I think it is about
1/8" larger. Its OD is slightly larger than the OD of a 1 1/2" pipe
coupling. There is no PVC pipe whose size is between 1 1/2" and 2". You
either have 1 1/2" pipe or you have 2" pipe. There is no 1 3/4" PVC pipe
and it would be too large if there were such a pipe.

So, what is the size of this drain?