Coffee – Does water “go bad” in this sense


I have an electric water boiler in the kitchen. I put fresh tap water into it, boil it up, and use it for my coffee. Then, an hour later, I go back and press the button again and have it re-boil the now room-temperature water, and use it for another cup. Sometimes, several hours pass; sometimes, half a day.

When "too long" has passed, I tend to empty it and put fresh tap water into it, because it feels like it has "gone bad".

Is this silly? Can water really "go bad" like that? Is there any difference whatsoever between freshly poured water and water that has been standing still in the container half a day or even the entire day?

It's still gonna be boiled? Doesn't that "neutralize" basically any kind of water?

Best Answer

It doesn't go bad, but it does change the taste.

When water is just sitting there, water evaporates, but most things dissolved in it don't. Then, each time you boil it, the steam causes additional water to escape leaving the same amount of dissolved stuff in there. So, the concentration of dissolved stuff keeps going up.

Dissolved oxygen also decreases when you heat or boil water, changing the taste.

Finally, even if your kettle is stainless steel, it can eventually rust.