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 evaporates from the glass over time, potentially leaving a higher concentration of everything else (minerals, chlorine, etc…)

When exposed to air and light, the water in the glass can … well, grow stuff.

The water in the glass can absorb stuff from the air… dust, scents, etc…

So first off the water in your tap isn’t sitting around for months. It came pretty recently from a water treatment facility of some kind and stayed mostly sealed away from air and light and odors and dust until it got to your tap.