shannette. You said that you come from OZ, Unless you have an Owner Builders License, The builder should have this information and he should also know that it agin the law for you to dabble in Plumbing unless it is just the layout that you need, the layout is to your discretion provided the areas and ventilation is allowed for.
If you are a Owner Builder then the full responsibility is on you to make sure that you employ licensed persons to carry out this work & it is them wots responsible for adhering to the regulations.
In most areas a basin can be deleted providing a laundry tub is provided, however laundry facilities must be provided for habitation.
Ime sorry Shannette but Health is considered a priority in OZ.