1) Tap water leaving the processing plants do meet international standards. In a local documentary on this subject (by TVB, available on Youtube, in Chinese), a water authorities official drank a glass on camera, while inside the facility

2) The same official went on to say that because of unknown maintenance standards/quality of water storage tanks and pipes in buildings, it is advisable to drink only boiled tap water

3) No genuine local drinks straight from the tap at home. Some would even drink only filtered and boiled tap water. Drinking fountains in schools, gyms etc. supply water that's filtered and/or UV treated.

Many of my friends tend to have upset stomach after having cold drinks with ice cubes in cheap local independent restaurants ("cha-charn-tang" ,not large chains or upscale places).

I always brush my teeth with water straight from the tap, never a problem. But I would never drink straight from the tap.