![Stewie D](https://www.homeone.com.au/img/avatar_h1_25x25.png)
Not sure if they mean drainage pipe sizes for vanities, sinks etc or floor wastes.
It was a bit confusing.
If it was the floor waste, why would the SS have referred to 50mm when there was at least one other larger one already fitted? He would have to have known if only from experience.
Two or more floor wastes in the laundry?