Do you not brush your teeth with this water? If so, I'm sure you realize that by doing so your mouth is absorbing some of the mouth along with your tongue and your cells, etc. In fact, you may even swallow some of the water without noticing. Not a whole lot, but enough to make yourself ill if this water were from the streets in Africa or something contaminated with malaria.

My point is, if you feel safe enough to brush your teeth with the hotel tap water, I'm sure drinking it in moderation is okay. Just don't make it part of your daily diet.