Originally Posted by
Scifience
FWIW, I almost always use tap water for brushing teeth and rinsing my toothbrush, even in most Tier 3 places, and certainly wouldn't bother in a Tier 1 city. I've got a bit of an iron stomach, though, and also used the tap water in places like Bangladesh with no ill effects...
This is one of those things where you can quickly drive yourself mad if you worry about it too much: i.e. what about accidentally swallowing a bit of water in the shower? Or maybe that restaurant washed the dishes in tap water and some got left behind? I'd be more concerned about the dangers of Chinese traffic and the chronic "fog" that engulfs most cities than any bacteria in tap water.
I've always just assumed that the likelihood of getting sick from incidental consumption of very small quantities of non-drinkable tap water (i.e. from rinsed veggies, or brushing teeth) is very small, and I've never really worried about it. I've always thought that the body can generally handle most small-scale incursions from the bacteria in reasonably clean tap water, and that as long as you don't drink it, you should be fine.
I've been brushing my teeth in Taiwan tap water (which is supposedly unsafe to drink) for almost 30 years without any problems. And I've never hesitated to eat raw veggies and salads here. But they generally practice reasonable food prep hygiene here.
On a recent trip to India, however, I was quite concerned about the lack of basic food prep hygiene, and I avoided anything raw (except for fruit I could peel), and used bottled water to brush my teeth. But I still got very sick from the food.