I doubt it's a nocebo effect when you can even smell the difference. I have a reusable metal bottle and can tell when I've refilled it straight from the tap vs. a filtered water source.

My wife is a good example. She absolutely refuses to drink water from the tap -- and we live in Portland, Oregon, which arguably has some of the purest water in the USA.

The point has been made several times in this thread, but some of this may be a matter of what you expect water to taste like. I grew up in a small town where the water had a kind of "mineral-y" flavor to it, and tap water in most places tastes a little off to me by comparison. I know that doesn't mean there's anything wrong with it, though.