Why will water start to taste bad when you leave it in a glass for too long, but will taste fine when you dispense it out of a tap where it’s been sitting for months?

Question

If you leave water in a ceramic, glass, or cup it will start to taste bad after a day or two, even if it’s covered with a lid. However, when we pour water out of a tap into a glass it will taste fine, even though it’s been sitting for days/months in a water reserve tank. Why is this the case?

In: Other

Answer 1

Water “fresh” from a tap is also typically [aerated](https://en.wikipedia.org/wiki/Aerated_water), instead of flat. And cold water can hold more dissolved gases. Room temperature water that has been sitting out for awhile usually doesn’t taste as good as cold, aerated water.