I recently suggested to my boss (one of the least scientific people i know) that we buy a tabletop hot water carafe/dispenser that keeps the water hot all the time. (Right now, folks who want to make tea just use the microwave to heat tap water.) He responded that water sitting in those carafes becomes “de-oxygenated” over time, and thus somehow unhealthy to drink. When pressed, he couldn’t come up with a reason it was more unhealthy, but said it was “obvious.”
While it’s obvious to me that the dissolved oxygen content of the continuously heated water could go down over time, i don’t understand how that water would be any less healthy for me to drink. Web searching for “oxygenated water” and health turns up far too much pseudoscience for me to wade through. So what’s the story? Is there any truth to his claim that de-oxygenated water is bad to drink?
It’s not as if you’re going to boil out the oxygen and be left with just a bunch of liquid hydrogen or something. Don’t worry about it – water that’s been heated continuously isn’t going to harm you, as long as the vessel was clean.
Can’t speak to the health effects of oxygenated/deoxygenated water (guessing there aren’t any), but hot water is going to have less O2 in it, whether you keep it hot all the time or heat it up just before you drink it. Assuming the water is saturated with O2 when it comes out of the tap (and I’m not saying for certain that it is), the water will continue to be at saturation (at a lower and lower level) as its temperature increases. Basically the O2 content will be the same whether you microwave it just before drinking, or pull it from a carafe where it’s been sitting hot for the past few hours.
I would think, purpler, that a “boil on demand” unit is a lot more energy-efficient than keeping the water at boiling temperature all day long. Or are you making tea with water that’s not at boiling temperature?
I use one of the tabletop units to boil water on demand, and will often fill it, bring it to a boil, make tea, and then boil the water that’s left an hour later for another cup. It may take me four cups over the course of the day to empty it. I have never noticed a difference in taste from the first cup to the last.
I’ve heard this before but can’t see that boiling water twice makes any measurable difference to mineral concentration, since such a small amount of water is lost as steam.
It’s not the reduction in water volume. I can’t remember the details, but there is a reason why heated water becomes hard water. Something about the way that heated water converts calcium salts into an insoluble form which then precipitate out when cooled.
Heated water doesn’t become harder. But when you heat the water, you drive off free CO2. This in turn makes the pH rise, and the remaining bicarbonate is converted to carbonate which precipitates with calcium to form CaCO3.
In fact, the water is harder before you’ve boiled it and precipitated out some of the calcium. Just get a water hardness measurement kit and do the analyses, and you’ll see.
ETA and just FTR: The stuff about “oxygenated water” (or “water with active oxygen” or whatever) being particularly good for you is utter bullcrap. For you, that is, not for the company which makes good money by selling plain water in fancy bottles at ridiculous prices…
A quick two-cents’ worth here: Pure Water (that is, nothing but DiHydrogen MonOxide molecules) is perfectly healthy to drink. You can make it by distilling any reasonably clean water. The downside is, it tends to taste “flat”, since most of the qualities we associate with good-tasting water derive from trace minerals and dissolved gasses, including Oxygen. There is no way any amount of heating could make the water “harder”, since the term hardness, when describing water, denotes the concentration of dissolved Calcium in the water, expressed as CaCO[sub]3[/sub]. If heating it makes the Calcium precipitate out, the water would become softer.
The only thing we require from water is the actual H[sub]2[/sub]O molecules. There is nothing unhealthy about drinking water without dissolved solids, gasses or other “impurities.”
(DHMO: Water Treatment Technician with over 17 years’ experience in the field.)
