Fact or fable: you should never boil the same water twice

By on March 21, 2019

A lot of articles on reboiling will say the following: when you reboil water, dangerous components will gather in the water instead of escape from it like it does normally. The following harmful substances are said to be found in reboiled water: arsenic, nitrates and fluoride. Would you buy a bottle of water that says “contains arsenic” on the label? Of course not! So why would you reboil water if you think there’s a chance it might contain arsenic afterwards? Healthy minerals will continue to exist in boiled water, but they could become dangerous when you reboil it several times. Calcium salts could gather in the water and cause gallstones and kidney stones.

To get to the point right away: reboiling drinking water is not dangerous. So, what’s the deal with this? It’s indeed possible for harmful substances to amass in water if it’s boiled several times. The drinking water we consume does indeed contain arsenic, nitrates and fluoride, but in such small quantities that it cannot lead to health risks if it’s boiled more than two times.

It only gets dangerous to consume reboiled water when 10,000 litres of water gets boiled down into only one cup of coffee or tea. Which is something nobody ever does, of course. So, the next time you’ve boiled some water and forgotten about it, don’t hesitate to simply reboil it. You can safely drink that cup of tea – it won’t do you any harm.

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