I remember living a month in Tokyo back in 2006 (or was it 2007). The house I shared had this toilet where the wash basin drained into the toilet tank. The fauc

I remember living a month in Tokyo back in 2006 (or was it 2007). The house I shared had this toilet where the wash basin drained into the toilet tank. The faucet is activated when you flush the toilet. So once you're done with your #1 or #2, you wash your hands and the grey water is used to fill the tank. It was quite clever.