Water doesn’t “go bad” like milk or your 2015 New Year’s resolutions. It just gets lonely, picks up plastic friends, or hosts a bacteria party. Trust your nose. If it smells like a pool or a pond, toss it. If it smells like nothing—or better yet, like chilled mountain rain—drink up.
And if anyone ever tells you that water expires, remind them that the Earth’s water cycle is 4.5 billion years old. That rain on your roof might have been Cleopatra’s bathwater. You’re not drinking “old” water; you’re drinking history. Just keep it out of the sun and away from your uncle’s garage.