I do agree with the majority it is "safe" but tell me this, why do all major airlines provide bottled water for their crew?
Surely if it is then tap water should suffice?
Just playing devils advocate here....
Because as already mentioned the potable water, whilst perfectly safe to drink, does not always taste particularly pleasant. Also when you go to the lavatory on board and flush, and subsequently wash your hands, where do you think that water comes from?
The aircraft has only one water supply, the potable water. It actually makes sense to provide bottled water for drinking as much as possible as this then ensures adequate water supplies for hot beverages, and for supply to the lavatories.