Reboiling Water for Tea
The tea lover’s argument is that water contains dissolved gases that contribute to flavor development as tea steeps. Reboiling water depletes the levels of dissolved gases, thus making a less flavorful brew.
To see if this theory held water, we compared a control batch of tea made with fresh-boiled water with tea made with water that was reboiled after we let it cool for 5 minutes. In a second test, we compared the control batch with tea brewed with water that was reboiled after returning to room temperature. We repeated each test three times. Our findings? All the teas tasted the same, whether they were made from water that was boiled once or twice, whether only briefly or completely cooled.
THE BOTTOM LINE: The act of boiling water for the first time already removes so much of the water’s dissolved gases that continued depletion from a subsequent boil won’t be detectable. So if there’s water left over in your kettle, there’s no need to pour it out.