I've been to Shanghai a couple of times, staying at the JW when there. And I have been to other cities and areas in China many more times that that. I will say that I always "assumed" that the tap water wasn't going to be drinkable and took appropriate steps. But I did use the tap water for brushing my teeth and such. As far as I can tell (my last trip was a couple of years ago), I didn't get sick or catch something that resulted in any long term effect to me.