If you’re the sort of person who’s conscious of not wasting resources, it’s tempting to fill up the electric kettle once and keep boiling the same water over and over again until it’s empty. Well, you might want to opt instead for just as much fresh water as you need for just that one cup of tea.
But why? It’s just water. Boiling it purifies it, after all. So giving it a second boil should make it all the more sterile, right? Nope, in fact he exact opposite is true.
Let’s take a closer look at what happens when water boils. At first glance, you see it bubble and steam, but there is also something happening at the chemical level. By cooking the same water multiple times, the oxygen content changes and potentially dangerous substances accumulate. You can really taste this with tea. Tea brewed with fresh water tastes very different to tea made with water that’s been re-boiled.
Boiling water is a great way to kill bacteria, that’s true. But when you boil water over and over again, dangerous gases and poisonous substances like arsenic, nitrates, and fluoride can form as a result of the changed chemical structure. Various studies have shown a connection between this fluoride and the damaging effects it has on the nervous system and brain.
Keep in mind that the minerals found in water don’t evaporate. If you were to boil water over and over again until it had all evaporated, you’d find a crust of minerals is still there. So if you’re regularly drinking concentrated amounts of these minerals — calcium, for instance — it could lead to problems such as kidney stones.
So this is the reason why you really shouldn’t ever boil the same water twice. Obviously, it depends on how clean your tap water may be to begin with. Smaller amounts for your tea isn’t really a huge problem, but the accumulated effect over a long period of time is really what might be better to avoid. If you’ve boiled too much and would rather start fresh, let it cool and water your houseplants with it instead — it isn’t dangerous for them!
Interesting stuff, eh? More fresh water in your system is always a good thing and the fact that your tea will actually taste better is just a bonus.