Daniellam,
I noticed that as well!!
When I go to a Chinese restaurant, I make sure I go to the washroom before heading out.. One time I was out with friends and had to go to the loo at the restaurant before dinner, and let's say, I quickly felt ill when the meal started. I now avoid going to the washroom when going to china town..
As for good Chinese restuarants with "clean" washrooms" I can recommend Lai Wah Heen, in the Metropolitan hotel in Toronto.