This may sound like a silly question, but I've always wondered:

If I boil some water and use some of it and leave the remainder in the kettle, and then a few days later boil that same water again, will it taste the same as if I'd emptied the old water and boiled fresh new water?

I've got a habit of emptying the kettle water and starting with fresh water to boil when I prepare my coffee (using a French press), and I'm wondering if there's no good reason to do that.

For what it's worth, the kettle has a top (so I'm ruling out dust as a concern), and the water I'm boiling is tap water that's been through a Brita filter in a jug.

If the taste is different, what's the chemical or physical justification?

3 Answers 3


Yes, it is different. Two things happen: the dissolved oxygen boils out, and whatever mineral solids are in there become concentrated as steam evaporates.

  • 3
    Not that it's necessarily a bad thing. A little extra minerals in water can significantly affect coffee flavour, but depending on the specific combination, it can be for the better. There is a town near where I live where coffee made from well water on one side of the river tastes amazing. Coffee made from well water on the other side is unpalatable.
    – Eclipse
    Aug 26, 2010 at 18:48
  • 4
    The effect of losing dissolved oxygen is also well known in tea-making. Thoroughly boiling the water very quickly extracts the dissolved oxygen. For this reason, enthusiasts of green and oolong tea never bring the water to a full, rolling boil in the kettle. Instead, they wait until the water in the kettle makes a distinctive rumbling sound prior to actually boiling.
    – Angelo
    Aug 29, 2011 at 14:18
  • AIUI, gases will re-dissolve in the water after it cools, so it'll end up with the same concentration of dissolved gases that it had originally — having been boiled won't affect that. (However, that doesn't apply to the second point: if the water picks up minerals from the kettle, then it won't lose those over time.)
    – gidds
    Jan 3, 2023 at 23:28

If it tastes different, it is either evaporating and you're getting a stronger flavor of the same water you drink.

The other thing is that it may be picking up flavor from the kettle.


Dissolved air is eliminated when you boil the water. However this is only really an issue immediately after the water is boiled. Waiting for a long enough time will allow the air to reabsorb into the water.

  • 3
    And this matters why?
    – SAJ14SAJ
    Jul 20, 2013 at 2:04

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