The Canadian design Brac Grey Water recycling system takes grey water run off from your bath, shower and laundy and stores this water for use in flushing your toilet.  Why flush perfectly clean water down the drain when you can use grey water, it's an incredible waste of a precious resource.  IMO, These kinds of grey water recycling systems should be be made mandatory in all new homes.

Not sure if the Brac units are available in Australia yet , but there's plenty of other Australian grey water solutions around.