Dave, I used to lay over in Sao Paulo, Brazil quite a bit. I too had the same buring question, keeping me awake at night...so I tried the sink, toilet and tub. As previously stated, if the toilet shoots water at an angle, that's the way it swirls. BUT in the TUB and Sink, if you plug it up and let the water level go up several inches, you can indeed see a little vortex spinning the -other way- when you let the water out, at least that's what it looked like to me.