You may have already committed this mortal sin before of boiling the same water twice.
You may have boiled a water once and forget about it until it cool down and later on decided to boil it again for the second time. Or maybe, you don’t throw out left-over water and just re-boil it no matter what.
Do you know that this practice might be harmful. Here’s why:
Boiling purifies it. The composition of water changes when boiled, which is a good things as the volatile compounds evaporate and gases dissolves. And that is the reason why it safe to drink boiled water. But do you think giving it a second boil would make it more sterile? No, as a matter of fact, it is exactly the opposite.
Let us take a deeper and closer observation on what happens when water boils.
In the beginning, you will see it bubble and steam, but there is something that is happening in the chemical level. As you cook the same water over and over again, the oxygen content changes and potentially harmful substances start to accumulate.
Although, you can actually taste it with tea; Tea brewed with fresh water tastes differently from the water that has been re-used.
On the other hand, it is true that boiling water is a great way in order to kill bacteria. But when you boil water multiple times, harmful gasses and poisonous substances like nitrates, arsenic and fluoride can form as a result of the changed chemical structure.
Furthermore, studies shows that the connection between these substances and fluoride has harmful effects on the brain and in the nervous system.
Let us put in mind that that minerals found in water does not evaporate. Thus, if you were to boil water over and over again until it all evaporates, you will be able to find a crust of minerals which stays there. Afterwards, it is not just a drinking water anymore and the minerals that supposed to be good for you, like calcium for example might just create problems that may cause the formation of kidney stones.
This is the reason behind the question in which why you should stop boiling the same water twice.
Absolutely, it still depends on how clean your tap water may be. Although, smaller amounts for your tea isn’t a really big problem, but the accumulated effect over a long period of time is really what you should avoid.
So, if you have boiled too much water than what is actually needed, it is more better to use it as a water for your plants once it is cooled – it isn’t dangerous for them after all.