Until now, we've only seen the hand-basin-on-top-of-toilet-tank as a separate piece that is affixed to a preexisting toilet -- like the Sink Positive. And, in that scenario, the set-up always looks a little homemade, which doesn't inspire confidence when you're washing your hands over your toilet (something that probably shouldn't seem strange, but does).
With the Integrated Hand Basin from Caroma the sink actually looks like it belongs there -- it's seamless; it's part of the toilet. And, somehow, that's preferable to us. Do you agree?
The hand basin-dual flush toilet combination has the potential to save a lot of water (70% over an 11L single flush toilet and separate hand basin). You wash your hands with perfectly clean water straight from the same supply that runs to your kitchen sink, and what would normally run down the drain, runs into your tank and is used to flush your toilet instead. We like it ... now!