Ripping out a Champagne bath from the 70s in a renovation. Here is a pic of the abomination behind the toilet. I measured the outer diameter of the waste pipe going into the concrete at 133mm (5.25 inches) Either I have: A - Measured it wrong B - Or this is a defunct / old waste pipe standard from pre metric days? If B, will I need to rip it out and replace with a metric standard waste pipe? Any help appreciated!