Bottled Water is Bullshit
I drink the tap water. My infant son drinks the tap water (with each and every bottle of formula). There are places in the world where bottled water has its place, and there are places where it's a complete and utter waste of money. Turkey and Eastern Europe, just like the United States, falls under the latter.
My general rule of thumb is that when the locals are drinking the tap or well, I'm drinking out of the tap or well. Now, that doesn't mean that all tap water that I drink goes unboiled—because in places like Lima, Peru that certainly isn't something you do—but I generally follow suit with the local populous.
In Turkey, I'm breaking that rule. Although the water is clear, crisp and generally tastes great in this country, I haven't been to a single home in Turkey where the resident(s) didn't have a large jug of bottled water sitting on the floor of their kitchen (the size you'd commonly find within an office building).
Timur, my current CouchSurfing host, says that a service comes by and delivers one of these large tanks for a few dollars when he's finished with one. He finds it economical to buy in bulk like this, citing that he doesn't like some of the treatments they use on the water here.
But that's awfully generalized. Not a single one of our hosts could really give me a solid reason why they drink bottled water or avoid the tap—just that they had some mistrust of the municipal supply.
For those of you reading from the States, I strongly suggest giving this quick, entertaining video a watch:
( video: Bottled water is bullshit )
…I can taste the glacier…