Why Does Tap Water Go Stale Overnight? | Hacker News Reader

Why Does Tap Water Go Stale Overnight?

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50 pointsLukeB_UK39 comments

The article touches very briefly on many possible explanations without ever coming to a conclusion.

But I'm fairly certain it's the one they mention towards the end: the evaporation of oxygen and the development of carbonic acid. That's why putting water in a closed bottle slows down the process.

What about tiny dust particles getting caught in the water?

I've not noticed 'stale' water, so I'm a bit confused about the topic.

If what you say is true, shouldn't places which use lake water, or places with a cistern, have the same stale taste to their water? Or those who melt snow for drinking water?

You don't drink lake water without further processing... Or at least you shouldn't if you want your insides to remain that way. Well water has an enormous range of taste, wholly dependent on a number of factors, including the soil/rock type that the well is sourced from.

While it's certainly possible to get water borne illnesses, the likelihood of that happening is low. Otherwise humanity would have died out long ago. Quoting from http://bwca.cc/tripplanning/waterfiltration.htm :

> Thirty years ago, we didn't fret about lake-water microbes. We just drank the water straight or spiked it with iodine. Today, that is changed. Many of us grip our water filters and cautiously take a sip. In fact, Giardia and other water-borne pathogens often star in those scary mind-flicks we conjure from bears, bugs, and huge, wind-swept waves.

> Don't get me wrong. I'm not saying that six months of recurring diarrhea isn't something to ponder. Just don't panic if you swallow a mouthful of lake water. The Boundary Waters isn't a New York sewer. Much of the water is clean. The problem is, we can't distinguish the clean sources from the dirty ones.

> That's why I filter, boil, or chemically disinfect the water I use for drinking, washing dishes, and brushing my teeth. On the other hand, canoe-country author Michael Furtman has roamed the Boundary Waters for nearly 40 years, and hasn't treated a drop and has never been sick. He's not alone. Quite a few Boundary Waters old-timers and wilderness guides drink the water. But they are careful about where they collect it.

In any case, my water filter for camping is only a ceramic filter. It doesn't change the oxygen or CO2 levels. If TillE's proposal is correct, the output after filtering should still be 'stale'.

What you said about well water is true, but my examples were structured to avoid ground contamination. If you collect rainwater, and let it sit for a day, does it taste 'stale'?

But carbonated water tastes good.

"Carbonated water" is an acid-base mixture, with more than one part of the mixture had "carbon" in it: https://en.m.wikipedia.org/wiki/Carbonated_water

Just adding acid won't give you the pleasant taste.

Also, humans ofte dislike trace flavors, even when they like the flavor : it subconsciously tastes "dirty".

'Also, humans ofte dislike trace flavors, even when they like the flavor : it subconsciously tastes "dirty".'

Interesting. This makes a lot of sense to me. I sometimes dilute fruit-flavoured soft drinks to reduce the calorie load, but there's definitely a point when they're mostly water where they suddenly become slightly unpleasant. Like, say up to 90% dilute is fine-to-nothingy, and 100% water is of course fine, but 95% dilute is worse than either.

(See also reusing a soft drink bottle for water without rinsing it first.)

My conclusion: warm, de-gassed water, like warm, de-gasssed beer, doesn't taste too good.

"The article touches very briefly on many possible explanations without ever coming to a conclusion."

Agreed, which makes the "...and now you know the chemistry of why" closer all the more infuriating.

I also agree that the evaporation/infusion of gases seems a likely explanation, because I've noticed that if I leave the fan on overnight near my glass of drinking water it starts to taste unpalatably stale a lot quicker. At least, it does to me.

Solution: start mountain biking. You'll be drinking warm, dirty, old water from old bottles and finding it delicious in no time.

I leave tap water in a carafe in my refrigerator overnight before drinking it, and even that tastes dramatically different when warm than when fresh out of the fridge.

Most faucets have aerators. Flat water has a distinctly different texture that aerated. For instance, if you're really thirsty, you can chug distilled water (which seems to have much less dissolved gases) rapidly, but spring water will not go down as smoothly.

Scientist note: Do not drink distilled water, at least not as a significant portion of your water intake. Water contains clinically relevant amounts of minerals that are important for health [1]. Fortunately, most "distilled water" sold as drinking water actually has these minerals added back in.

On a related note, really dont drink deionized water (you can think of it as ultra distilled, also the process does not necessarily involve distillation). Aside from tasting extremely nasty (dont ask), sufficient quantities are extremely dangerous. Fortunately it is expensive and generally only available in labs.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1495189/

Water can contain clinically relevant quantities of minerals, but as the article you linked states it is secondary to food. Some regions have naturally very soft waters (famously Pilsen, Czech Republic, where it is an important part of Pilsener beer). Those waters don't have clinically relevant mineral content, but people there don't have mineral deficiencies unless their diet is also mineral deficient.

I've heard your claim that drinking ultra-pure water is dangerous many times before, but I've never seen any citation from a reputable journal. It seems highly implausible to me, as the ultra-pure water will cease to be ultra-pure immediately as it hits your stomach. In general it's very difficult to keep ultra-pure water pure.

You say that most 'distilled water' sold as drinking water has minerals added back in. Where do you get this information?

I live in China, where tap water is not considered safe to drink, and bottled (or boiled) water is the norm. In my experience, most brands of drinking water do not contain minerals. One of the premium brands (Watson's) actually has a separate 'with minerals' version, with a blue label instead of their normal green label.

Oh, and I've tested several brands of water with a portable TDS meter, and all registered between 0% to 5% of the values yielded from tap water at my home and my office.

The problem is with "pure" H2O. Water is REALLY good at dissolving things, which it does better if nothing is already dissolved in it. The warnings I have received Are the drinking completely pure water will leach minerals out of your stomach/intestines. There is a big difference then the "public" version of pure and the laboratory grade version of pure water. No water found in nature would be considered the latter.

I live in an area where water is drawn from aquifers within limestone deposits - I actually like the "taste" of hard water over soft, but when I leave a glass of water out for the night, I might also see flecks of calcium precipitant.

mine doesn't at all. ever. in fact i had some in a bottle behind my monitor for a year and it was fine

Incidental question, but does anyone filter tap water? If so, using what technology?

My area has decent water, but there are some issues. I tried bottled mineral water, which I found quite inconvenient and expensive. It's probably very harmful to the environment too.

I filter mine just to remove some of the taste the pipes add. I'm not sure if you're looking for something fancy, but I use a basic Brita water filter. The best thing to make water taste better thought is to chill it in the fridge though.

Charcoal based filters, like brita, or the ones built into higher end refrigerators are cheap and effective. I've used them for years, though the effect on taste might be a placebo, and the water in our area certainly isnt unsafe.

Of course, it depends what "issues" your local water has.

Well, there are always traces from some heavy metals and excess of chlorine for example. I was thinking about a gravity or a reverse osmosis filter. Surprisingly some studies I've seen came up with very good figures in case of rather simple gravity filters.

According to Brita they remove chlorine and cadmium (a heavy metal), amount other things. [1]

As near as I can tell, "gravity filters" work on the same priciple as Brita filters [2].

[1] https://www.brita.com/why-brita/what-we-filter/ [2] http://www.phoenixwaterfilter.com.au/images/stories/phoenix/...

P.S. I have never worked for Brita and havent used their products in years, so please dont take my comments as shilling.

I used to use Brita filters for a long time but one day I looked closely and noticed tiny dark flakes in the water from what I assume was charcoal from the filter. Using new filters still left the flakes in the water so I just stopped using them altogether. Now I've been drinking straight tap water for ages. The taste was noticeably different at first but the tap water is perfectly safe where I live and it saves money.

I still wonder if it's normal for those charcoal flakes to pass through the filter and into the drinking water, and do they pose any concern?

I still wonder if it's normal for those charcoal flakes to pass through the filter and into the drinking water, and do they pose any concern?

Yes, no, and if you soak the filters beforehand as the instructions say, there are less flakes.

> I've used them for years, though the effect on taste might be a placebo

Personal anecdote that it may not be placebo:

I find the tap water where I live (Northern part of NL) pretty delicious. In fact I can hardly distinguish it from most non-carbonated bottled water, it's just clean with no particular flavour I would recognize (though maybe I'm used to it). When I visited the US (NY and New England area) I found the chlorine taste quite noticeable, also a slight dusty/earthy flavour (I didn't complain, and it was a hot summer).

However, one of the people we were staying with brought one of those plastic jug/caraffes with a built-in filter (probably charcoal), which she filled with tap water. I really didn't expect it to make much of a difference, because how was a tiny filter going to take chlorine molecules (not ions, right?) and that dusty flavour out of the water, that quickly, just by pouring through? (apparently I have no idea how these filters actually work, and a little voice in the back of my head dismissed it as some weird health fad thing)

Well, I was taught :-) I was pleasantly surprised when I found that the filtered water tasted "clean", pretty much just like it tastes back home. But since I really didn't expect it to taste much different than straight out of the tap, actually half-expecting the filter might make it a bit more "stale" (assuming it would mostly take out some of the CO2 and O2 gases), I doubt that could be placebo, wouldn't you agree?

On the other hand, placebo effect can be really weird, in your head, even if you really believe it's not affecting you, so I'm not going to presume there was no placebo going on. I also didn't think to try a double-blind test or something, instead happily enjoying the refreshing filtered water during a hot summer :-)

At my home, I use a filtering faucet with a carbon filter (the same thing you see in those filtering pitchers, or some fish tank filters). Mid-tier refrigerators that produce chilled tap water frequently include this kind of filter.

I installed an ultraviolet sterilizer before the filter. This has no effect on the taste, but it does prevent most sorts of pathogen from colonizing the filter. This isn't generally an issue, but we felt like it made sense to add this when we installed the filter anyway.

At my office (same municipal water source), we have a very fancy reverse-osmosis filter. This is the same thing most of the bottled water companies use. I slightly prefer the taste of this water, but I think this is just because it's colder. The device is much more expensive initially ($200+, vs. $10 for one of the pitchers or around $50 for an under-sink carbon filter).

I filter tap water with replaceable brita filters.

Not because it tastes bad, but because tap water around here is hard as hell, cooking pasta once or twice with unfiltered water is sufficient to leave traces in the pan (and yes pans get washed), limescale starts building up in the kettle in a pair of days (though to be fair between coffee and tea the kettle runs 6~8 times a day). Brita filters is the only thing I've found yet which gives me a month between vinegar-rinsing of the kettle (and yes, the filter dies in ~a month, start letting shit through and limestale instantly starts building up in the kettle, it's a right pain in the ass)

Your question... surprised me.

I am from Brazil, here everyone filter their tap water.

Also my Startup associate is from France, and he claims in France this is also true.

As for what we use:

This is a classic: http://www.precolandia.com.br/images/product/279021A.JPG

Water filtered with those clay filters (the filter itself is made of carbon, not clay) somehow always feel fresh, sometimes on extremely hot days I can swear that despite having no active cooling, the water that comes out is cooler than the air.

Also this is common: http://www.decorandoimoveis.com/wp-content/gallery/filtro-de...

My mother has this one: http://mlb-s1-p.mlstatic.com/elemento-filtrante-filtro-agua-...

It is really good, but very expensive.

Water from unbaked clay filters feels fresh due to evaporative cooling [0]. Some of the water seeps through the walls and slowly evaporates, cooling the recipient. The magnitude of this effect depends on air humidity. This is the same principle behind a Botijo [1].

I don't know where in the country you're from, but here the water and sanitation department said the water is okay to drink from the tap. Very few if any people do it anyway, as everyone is used to filtered water. Maybe water quality wasn't as good in the past, or as reliable (it still isn't).

[0] https://en.wikipedia.org/wiki/Evaporative_cooler

[1] https://en.wikipedia.org/wiki/Botijo

Hum, you're associate is not right. I'm from France and I don't filter tap water (nor the majority of people I know). You do find people that do it, but I wouldn't say it's the majority.

I've always lived near the Great Lakes in the US, and in general have never felt the need to filter our tap water.

That said, I know others who do (either charcoal or reverse osmosis).

I have friends who live on the east coast and they claim their tap water is awful and they typically drink exclusively bottled water.

My family has a reverse osmosis filter and it tastes identical to bottled water despite the tap being extremely hard well water. Depending on how much water you drink, it should pay for itself in a couple months. I think ours was $250.

I'll second this. I can actually enjoy drinking water when it comes from my RO system.

does anyone filter tap water?

We do, via refrigerator filter, even though we have very good water in this area (from Mt. Hood).

Other areas of the country aren't so lucky. Sometimes municipal water may come from[1]:

   a sewage treatment plant's outlet 2 miles upstream

400,000 people got sick, 100 people died.

[1] https://en.wikipedia.org/wiki/1993_Milwaukee_Cryptosporidios...

Tap water also contains chlorine or chloramine which evaporates fairly quickly (chlorine much quicker). That may affect the taste directly or indirectly by allowing other bacteria to grow in the water.

+ water quality can change fairly quickly (eg. overnight) source: im a founder of water quality monitoring company

The water in Berlin tastes better after sitting for some time.

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