There weren't any problems with Chinese milk or baby forumla either until someone decided it would be a wonderful idea to put melamine into it.
In my view, the chances of there being an issue with the mains water supply in HK are very low, but the impact very high, so I take reasonable precautions. I still use tap water for brushing my teeth, showering, washing clothes etc as I'm sure even if someone did decide to poison our water supply a little exposure wouldn't kill me.