eli5: Why can’t you drink Demineralised Water?

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At my local hardware store they sell something called “Demineralised Water High Purity” and on the back of the packaging it says something like, “If consumed, rinse out mouth immediately with clean water.”

Why is it dangerous if it’s cleaner water?

In: Chemistry

19 Answers

Anonymous 0 Comments

Demineralised water is different from distilled water. Two big differences are (1) demineralised water is not treated for bacteria/viruses because it’s not intended for drinking, and (2) drinking demineralised water will actually leech minerals like calcium out of your body. Even pure water has trace minerals, which are essential for our bodies, whereas they are not present in demineralised water. Distilled water is fine to drink, although spring/tap water is best.

Anonymous 0 Comments

The leeching out minerals and osmosis causing cells to burst thing is a myth. You can drink 100% pure water with no ill effects, provided you dont drink too much…which is equally true of ordinary water.

Anonymous 0 Comments

The demineralized water at the hardware store isn’t rated for human consumption.

Selling drinking water requires you bottle it in food safe bottles, in a sterile facility that has been inspected, while getting your water from a safe source that has been tested.

Demineralized water generally starts with perfectly safe water from a municipal source, but it’s bottled on equipment that they don’t bother rating/inspecting for human drinking. It’s cheaper to just put a tag on it that says NOT DRINKING WATER.

Anonymous 0 Comments

It isn’t. Demineralized water is exactly what it sounds like – water that has had the trace minerals removed by one of a number of different purification processes. It’s perfectly safe to drink.

However, there have been myths about the dangers of consuming it for years for a couple of reasons. First, most people are used to drinking water with trace minerals, so to many people pure water tastes like, well, nothing, which is both weird and noticeably different from what you’d expect. Second, pure water is slightly acidic, which is why it dissolves those trace minerals in the first place. It’s fine to drink and far less acidic than other things we consume, but it will fairly quickly eat through metal pipes or containers that are in constant contact with it. Third, it’s primarily used for research and industrial applications, not drinking.

You give people weird-tasting water that eats through metal and is used in making car batteries and tell them it’ll also mess with their body and it sounds pretty plausible. I would assume the answer to your original question is that the store/manufacturer put that warning in order to comply with regulations about bottling water for human consumption vs other purposes and/or to avoid frivolous lawsuits, which are expensive and a pain even if they’re completely baseless

Anonymous 0 Comments

I spent years in submarines drinking distilled water. Do I get disability?

Anonymous 0 Comments

Depends on the purity of demineralisation. DM water usually contains 1-10m/L (ppm). Generally safe unless you’re exclusively drinking it

100% demineralised will definitely cause massive harm though, because it’s so hypotonic. Your cells will start absorbing water. This disturbs the balance of electrolytes (electrically conductive ions) in your body. This is most seriously a problem in the brain, where water poisoning can lead to brain damage, coma and even death.

Anonymous 0 Comments

Honest question related to this topic:

My tap water has lead in it (old pipes), so I installed a reverse osmosis system under the sink for obvious reasons. It came with a system for remineralizing the water, and alkalizing it, but the connection kept leaking, so I just hooked it up directly to the dispenser, essentially making it so the water we drink comes directly from the reverse osmosis.

Thoughts?

Anonymous 0 Comments

Because it will try to remineralise using your minerals. That would be bad for your body and skeleton.

Anonymous 0 Comments

In a lot of cases labels are put there because an ignorant lawyer in the legal department figures that we need to do something “just in case”. You can’t really explain them that if a water would be toxic then mouth rinse would not help much. This “do something” mentality and “better safe than sorry” ideology leads to a lot of totally nonsense rule and label. Anyways, rinsing your mouth does nothing except making someone happy in the legal department.

Drinking distilled or deionized water in general is not terrible problematic. The two reasons why it’s told not to drink are as follows.
In chemistry class it’s banned from drinking for safety reasons. You never know what contamination may have left in a vessel or dropped into the otherwise distilled water, after distillation. So it’s kind of “do not drink or eat anything from the lab, ever ever even if it is labelled as distilled water or normal salt or whatever otherwise edible thing”. Unfortunately there are always those few idiots whom you cant just simply ask not to, so you indoctrinate the big red ban label with word of power. And then many people remember only that “there was something in chemistry lab about not to drink distilled water because toxic”.

The other thing is that even though you can consume distilled water it indeed ultimately washes off salts from your body. But it’s not like you drink a glass of distilled water and you drop dead. It is about the balance, and if you eat very salty and mineral rich food, then some distilled water is perhaps even better. Your body doesn’t know if the salt comes from food or the water. It may be a problem on the long term if you eat mainly sodium chloride and no calcium and magnesium because those would come from the water at some extent and so with d-water and salty chips you get both salted and unsalted. The real problem occurs however if someone does intense sport and with sweating they lose a lot of salt. Water poisoning can happen if they drink pure water in large amounts and suddenly. This is when you suddenly dilute the leftover minerals by drinking water. It can happen even with normal drinking water but much faster with distilled water. The thing is that you never know your salt levels and you can’t undo drinking a liter of d-water. So if you don’t know exactly what you do, it’s safer not to.

So again, in certain conditions it’s absolutely no problem to drink deionized or distilled water if it’s otherwise pure (in terms of bacteria for example). But for those few cases when stupid people do stupid things and you as water seller may be held accountable, you are safer to just put a big general ban on it. Because it’s always better to be overly salted and your kidneys will sort it, than being in low mineral shock and your heart stopped before your kidneys had the chance.

Anonymous 0 Comments

Ignore all the old wives tales bullshit.

Demineralised water is perfectly safe to drink, assuming the water is not microbially contaminated.

Also distilled water is safe to drink.

Demineralised water from a  hardware store is simply not rated for human consumption, because no one cares if there‘s some E. coli in there for the purposes of putting it in your iron.

The amount of minerals in drinking water ranges from next to zero minerals, to tasting extremely chalky. People who live in areas where the water is very soft aren‘t harmed.

The amount of minerals in drinking water are just one hundredth of that found in regular food.

The only actual use for minerals in water is calcium in them, because spreading out your calcium intake throughout the day allows more to be absorbed.

If you drink a litre of calcium rich mineral water at once, you can just as well eat a slice of cheese or drink a glass of water.

If you demineralised water that’s clean or distilled water yourself, you can drink it for the next decades, until whatever cause of death takes you: the water makes zero difference.