I on average drink 120-150 oz of water a day (sometimes a portion of this is unsweet iced tea, or diet soda), since I started doing this, I've lost weight and generally feel healthier. So several years ago, I got in the habit of lugging around a large beverage container (http://www.whirleydrinkworks.com/productinfo.php?prod-code=X...) 9 times out of 10 its just tap water I put in the thing. I only drink bottled water when I'm in a position where I can't get access to fill my beverage container from the tap - or when due to security or other factors I'm unable to bring my large beverage cup, but bottled water is allowed.

Bottled water (usually purchased in a 1.5l, 2l or 1gal container) is something I purchase only for convenience when I simply don't have access to any tap water at all.