The water in Russia is terrible. So terrible and unsafe to drink, in fact, that you will not find any water fountains anywhere. There is no such thing as a free glass of water. In restaurants, if you want water, you will pay for bottled water. Many people are seen carrying their own bottled water (or alcohol, pepsi or juice). Wherever you go BYOB. We are paying a lot for bottled water because we go to restaurants a lot due to our schedule. (there are two kinds - still or gas.) Gas means with bubbles. If you are fortunate, you can get a bottle of COLD water. Russians don't like their water cold.
Fortunately, the mission office and all of the missionary apartments and church buildings are furnished with water filtering systems which we install for safe drinking water. You do NOT want to drink water out of the tap. There will be an excellent chance that it will make you very sick.