'Which brand of water do you drink?' is a perfectly valid sentence. You would probably use this if you want to ask someone which brand of bottled water they drink.

There is nothing wrong with that as it implies that you want to know the manufacturer of the water if may say. However, the common question is What type of water do you drink? referring a natural water, spring water ...etc.

I think you are very serious in learning English. Today I saw many questions from you.

There is a well in my house. We take water from that well.