It depends where you live but in general, national guidelines call for 0.2 ppm, that is parts per million, so if you had one million glasses of water, then one of those glasses would have a bit of chlorine it it. 1/5 of that glass (0.2) would have chlorine out of one million glasses.

However, chlorine reacts with other things along the way, and it also goes into the air very easily, so if you let a glass of water sit for a few hours, most of the chlorine will be gone.

Chlorine is added to kill bacteria that naturally occur in water that can give you tummy aches and give you diarrhea.