In many places you can read that it is better not to drink the tap water so buy minneral water.
You can find minneral water almost everywhere but the best option to buy water is is a supermarket - they are cheaper there.
we bought 6 bottles (1.5liter) in 4.5 YTL while outside (on the touristic places) it cost 1-2 YTL for one bottle (0.5 liter).
I am a frequent visitor to Istanbul. I would advise all visitors to bursh their teeth using bottled water too. I used to always have an upset stomach when visiting... nothing major, though. Since I also started brushing my teeth with bottled water while in Istanbul, I have been just fine. Just a suggestion so you can all better enjoy The Most Beautiful city in the world.
During summer months water may be scarce in the parts of town that are set most uphill.
When I visited there was a water shortage in the district around the Galata tower, where trucks were distributing water to the local families every evening.
You will see people (usually little boys) selling water and lemonade on the streets. They often only have one glass from which everyone drinks from. And they either dont wash the glass at all or just rinse it with some water.
Hey all. I've noticed that everyone is being quite vigilant about using bottled water for things. I moved to Istanbul a couple of weeks ago, and I've used the water to wash all of my fruits and vegetables as well as to brush my teeth. I haven't had any problems in the least. Especially if you're used to being in slightly less developed areas (I've lived in China and Southeast Asia before), you will not have any problems as long as you don't ingest large quantities of it. My suggestions are to not bother brushing your teeth with bottled water - it's a much bigger hassle than it's worth, but you should probably stick to bottled water for drinking, unless you want to boil the tap water.
Drink bottled water, and make sure the cap is sealed. I did get one bottle of what was probably (bad) tap water refilled into a bottle. Not all the water is bad, but it's easy to get sick if you aren't used to it.
There was some question about the safety of the tap water when I was in Istanbul. I used it to brush my teeth and wash my hands and drank bottled water. Use the same precautions you would use anywhere else with fruits and vegetables.
DONT DRINK THE WATER. In all the literature we read before we got there it said not to drink the tap water. Only bottled water shall be used. However, when you arrive in Istanbul, and eat out at a local restauarts everyone serves bottled water. Not even the locals drink the water, so there's no need to keep asking if its bottled water.
I regularly drink tapwater here in Istanbul, using it also to brush my teeth and wash my face. The only things that have gotten me sick here in this city are alcohol and eating cold chicken from a cafeteria. If you want to play on the safe side and drink from a bottle, good on you, but this isn't India and nothing bad is going to happen if you're not wrapping your lips around a faucet and trying to drain the Bosphorous.
One of my guidebooks stated that drinking water from the tap was not such a good idea, I still brushed my teeth with it but for drinking water we found a guy selling cold 1.5L bottles for 1tl (about 50 cents), for me it's not worth the risk of getting sick, certainly not with bottled water being so cheap. If you don't want to lug around a giant bottle of water, bring a smaller water bottle to fill up. But in the heat of July we were drinking 2 or 3 big bottles of water a day.