Does a glass of water become too old to drink?

September 5, 2015 4:42 PM

This is a "who's doing it the normal way?" question. I prefer not to drink glasses of water that have been sitting out for more than a few hours because I find that the taste gets worse with time. My girlfriend thinks this is the most ridiculous thing she's ever heard and that the idea of "old water" is absurd. Which of us is more conventional?

I don't think that water that's been sitting out is particularly nasty on the scale of nasty things. However, when thirsty and confronted with a glass that's been sitting out, it's almost always easy for me to just go pour a new glass of water, and I will always do that in preference to drinking the water that's been sitting around. I'm not so insistent that I'd refuse to drink a glass of water that I've left by the bedside when I wake up in the morning, but that's probably the oldest water I drink outside of exceptional circumstances. I'm sure that I often throw out water that tastes fine, but I err on the side of caution. If water has been left out for a while - say, I am confronted with a glass of water that I left out two nights ago - I wouldn't drink it. And, to be clear, this is only true of water that's in an open container. If it's in a water bottle or something it's fine for a longer period.

My girlfriend says that if water has been sitting out in a clean house without pets, it's fine to drink. She says that it will not get nasty even given several days.

posted by vathek to Food & Drink (52 answers total)

Haha, I asked the same question a few years ago.
posted by ellenaim at 4:45 PM on September 5, 2015 [1 favorite]

I'm with you, I don't like to drink water that's been sitting out for a while. It doesn't really have anything to do with safety, just that I don't like the way it tastes. But I prefer my water cold too, and water that's been sitting out will be (by definition) at room temperature, which is another strike against it.
posted by primethyme at 4:48 PM on September 5, 2015 [1 favorite]

Bacteria will eventually grow in a glass of water, but I personally have no problem drinking water that has been sitting in a glass for a day or even two. If anything, I prefer it, since all the residual chlorine or chloramine has evaporated by that point.
posted by wierdo at 4:50 PM on September 5, 2015 [13 favorites]

I firmly am in the same camp as you and can tell if water has gone flat or stale if it's been uncovered in a container for a few hours. If water's been in a bottle or enclosed jar, though, it's fair game. I do not drink tap water unless it's an emergency.
posted by Hermione Granger at 4:50 PM on September 5, 2015 [2 favorites]

Response by poster: My objections to old water are much more about taste than safety. I certainly don't worry that two day old water is going to make me sick. Presume for the purposes of this question that you somehow know that the water is safe to drink.
posted by vathek at 4:51 PM on September 5, 2015

I prefer water that's super cold, so I'll sometimes toss out what's left in favor of new and ice. But honestly it's got nothing to do with taste.
posted by clone boulevard at 4:51 PM on September 5, 2015 [1 favorite]

Of course it's still safe to drink water that has been sitting out for a few days. But it doesn't taste as good and I wouldn't drink it. I picture it getting dusty, but I think the main thing that actually happens is that it becomes less aerated and that affects its taste. I also can't help but think of the possibility of bugs falling into it. So I'm with you. If it's been sitting out for more than a few hours, I'll probably dump it and fill the glass with fresh water.
posted by Redstart at 4:54 PM on September 5, 2015 [17 favorites]

My guess is that freshly drawn water is better aerated, so although it's far from being carbonated it may have better mouthfeel in some way. Whereas water that's been out is room temp and any aeration will have escaped, so it tastes flat.
posted by zadcat at 4:55 PM on September 5, 2015 [7 favorites]

Every now and then I discover a half-empty glass of water that's a week or more old, and drink it. It may not be quite as tasty but I don't really notice.

Then again, I'll do the same with a glass of whiskey. Or wine. Or coffee. So maybe I'm the abnormal one. But I tend to think water just tastes like water.
posted by Erroneous at 5:00 PM on September 5, 2015 [4 favorites]

There is a definite difference in taste. Water that has been sitting for a while taster flatter and smoother to me. I think the difference is lack of chlorine and chloramine, plus changes in dissolved gasses.
posted by ssg at 5:07 PM on September 5, 2015 [1 favorite]

I'm the opposite, I prefer to leave water out for awhile, to get rid of the chlorine flavours. If there is water left in the electric jug, I'll grab it from that. I think most people are used to that flavour and have grown to prefer it.

I do think recently oxygenated water tastes very slightly better than flat, but if it's in a bottle, shaking it vigorously appears to achieve that same flavour.
posted by Elysum at 5:16 PM on September 5, 2015 [1 favorite]

At one point I was living in a basement apartment that later turned out to have roof problems and mold. If I left a glass of water out longer than a day or two it would literally grow mold. Obviously this is not typical but does escalate my caution when approaching water of unknown freshness! Glad I don't live there anymore.
posted by rubster at 5:17 PM on September 5, 2015

A few hours? That's fast to replace, in my book.
posted by J. Wilson at 5:23 PM on September 5, 2015

Yes, this is totally a thing for tap water and it happens regardless of where I am living, although the water from place to place does vary in taste. The tap-to-stale time runs about 3-5 hours. I'm sure temperature has a bit to do with it.

The tap water where I'm living now makes TERRIBLE ice but tastes great cold from the tap. Go figure.
posted by mochapickle at 5:24 PM on September 5, 2015

I am aware that there's a taste difference between fresh water and water that's been left out for a while, but I'm fine with drinking the older stuff - it doesn't taste "bad" to me. Come to think of it, I'm pretty sure I've drunk water that's been a few days old before, which makes me think that while "fresh and cold" tastes different (to me) than "not fresh and cold," the difference between "a little old" and "several days old" is less significant.
posted by DingoMutt at 5:30 PM on September 5, 2015

Well, I don't drink water that's been left around and unattended for even a few minutes, but that's because my cats like to come and dip their little poop feet in it. Besides that, though, I think water that's been sitting for a while loses some of its dissolved gases--that's what the bubbles clinging to the sides of the glass are. It's not impossible that this affects the taste.
posted by pullayup at 5:34 PM on September 5, 2015 [3 favorites]

If we refer this question to our feline overlords, they will generally agree that 'old' tap water is nasty. Cats (generally) prefer fresher water. i agree with them because it does get an icky taste and clearly, they are wise and have life figured out what with the all day napping and human bossing around.
posted by kitten magic at 5:36 PM on September 5, 2015 [13 favorites]

pullayup has a good point, the kitties don't like to drink old water but they do like to ensure no one else would risk it either.
posted by kitten magic at 5:42 PM on September 5, 2015

Water tastes terrible to me if it's been sitting out (in a glass - water bottles are fine) for more than a few hours. Now I'm off to read primalux's article to find out why...
posted by heisenberg at 5:50 PM on September 5, 2015

Ugh, I'll change water if it's been out for more than half an hour or so. It tastes stale, but moreover it has warmed up and that's disgusting.
posted by arcticwoman at 6:10 PM on September 5, 2015

I have a pretty refined water palate since I drink water almost exclusively (also coffee, the taste of which is greatly affected by the water used). Personally, I can tell easily if a glass of water has been left out for awhile. I will drink it; the sort of flat staleness does not bother me, but it is definitely unquestionably noticeable.

The way to test this would be to do a blind taste survey. You should both participate. It might be fun! It just sounds like your own taste is different from your girlfriend's when it comes to water.
posted by sockermom at 6:20 PM on September 5, 2015 [1 favorite]

I pour out water that has been sitting around because it doesn't taste as nice and that one irritating housefly has almost certainly been walking on the rim of the glass. It's not something that I think of as necessary, but when water isn't scarce I'd just as soon drink a nicer tasting glass of it.
posted by Dip Flash at 6:29 PM on September 5, 2015 [1 favorite]

I don't really like day old water because nyc is dusty and grimy and no matter how often I clean my AC filter/fans there's still dust everywhere in my house within a day or two. Why would my water glass somehow magically be dust-free?

pleh
posted by poffin boffin at 6:32 PM on September 5, 2015

We have fairly hard water here and I think it tastes *better* if it's been sitting out a while. My theory is some of the chlorine evaporates.
posted by Violet Hour at 6:38 PM on September 5, 2015

My daughter refers to this phenomenon as "dusty water". She is, it is perhaps worth noting, completely nuts.
posted by Sing Or Swim at 6:38 PM on September 5, 2015 [4 favorites]

Water straight from the tap has an extremely low chance of containing spiders. Water that has been sitting in an open glass for hours has a marginally higher chance of containing spiders. I think the choice is obvious.
posted by Faint of Butt at 6:42 PM on September 5, 2015 [9 favorites]

Sing or Swim's daughter is completely sane, water gets dusty like everything else, and tastes, no surprise, like dust.
posted by HotToddy at 7:10 PM on September 5, 2015 [3 favorites]

I drink day-plus old water. Sometimes I'm not even sure if it was my water in the first place, but it was either mine or my wife's so unless we've had company recently I'll just down it. We live in California, which is famously in the midst of a drought, so I prefer not to waste water. I figure every 8 oz glass of unwasted water buys me an hour or so of daydreaming time in the shower (give or take).

Oh, and the old water definitely sucks compared to fresh water, but it's still just an inoffensive glass of water, so who cares.

Sometimes I discover that it was not in fact my (usually tap) water, but (most likely) my wife's old carbonated water from the SodaStream. You want to talk about stale water? That is some stale-ass water because the very freshness of it has devolved into carbonic acid or something that is very much an additive that does not taste good. I drink it anyway. It's only mildly unpleasant and it's very important to hydrate.

Also, we have no pets and almost never have houseflies. If there were a fly around I might not drink water that had left my sight. Flies are repulsive.
posted by univac at 7:21 PM on September 5, 2015 [1 favorite]

I definitely taste a difference but don't actually have a huge preference (except that I like very cold water, which is balanced out by being quite lazy). I am not worried about bugs in my water as I can actually see any bugs big enough to bother me.
posted by jeather at 7:26 PM on September 5, 2015

I keep my water in a sealed bottle (a Camelbak). It still tastes "not like fresh" with no possibility of dust, spiders, flies, etc. But it doesn't bother me, so I drink it anyway (even if it was sitting on my desk overnight--however long it takes until the bottle is empty). It is mostly about temperature. Also, if you're accumulating an appreciable amount of dust on a flat surface over the course of a day--try vacuuming more.
posted by anaelith at 7:59 PM on September 5, 2015

I LOVE old water! I usually have a couple of water bottles hanging around the house filled with water from some point in the last week. I feel like old water tastes sweeter and feels more silky on the tongue? I dunno.
posted by joan_holloway at 8:07 PM on September 5, 2015 [1 favorite]

I keep water bottles in the bedroom for a sip or two at night and refill them at most once a week. During the day I prefer it cold, but at night I'm just trying to avoid that parched feeling.

I think it's pretty conventional to take a wasteful attitude toward water, so I'm going with the idea that you're more mainstream/conventional. In the last hundred years or so we've come to think of it as not precious , and most people comfortably luxuriate in the idea you can toss water out if it's not the perfect temperature and aeration level. That, of course, is a luxury in relative terms, but it's conventional to modern developed-country people who don't have to pump or filter or ration their water.

If you don't want to waste it, you can water plants with it, or toss it in a basin to soak dishes.
posted by Miko at 8:13 PM on September 5, 2015

60 now--I will continue to drink water that's been sitting in a glass for days without a second thought. Well maybe I will have a second thought now that I've seen this thread.
posted by rmmcclay at 8:14 PM on September 5, 2015

I wonder if it has to do with the fact that when it's been sitting out around the house a tiny little layer of dust or debris particles settles in the water. It definitely tastes different. You're not crazy.

BUT interestingly enough, I find water that's inside one of those adult straw sippy cup things with a lid perfectly acceptable to drink after several days unlike "open water". This might be related to the fact that I have a cat who can be discreet about unsanctioned water sippage and it's gross to drink after your cat.
posted by mermily at 9:01 PM on September 5, 2015

It is fine.
posted by AppleTurnover at 9:04 PM on September 5, 2015

I am with the I-like-water-that-has-been-sitting-out group. Like others have stated, it seems to allow the slight chemical taste to go away. There is a defined window of time though. If it has been sitting for days I won't drink it just because it is likely to have some dust particles that have landed in it, and then it is no longer just water.
posted by LilithSilver at 9:38 PM on September 5, 2015

Like others here, I always assumed the difference in taste was dust, and I prefer to get a fresh glass. Also, cats.
posted by Maxwell's demon at 10:10 PM on September 5, 2015 [1 favorite]

I drink a fairly crazy amount of water and over time have gotten lazy enough that i just drink it. On some level maybe I'd like a fresh glass and new water but who has that kind of time?

I've gotten to the point where I prefer it without ice, or with only one cube, which has led to a lot of in-house jokes about how I'm so old that an extra piece of ice will keep me up all night and I have to avoid that kind of excitement.
posted by A Terrible Llama at 1:11 AM on September 6, 2015 [4 favorites]

The head gardener in our community garden insists we use water to water the plants which has been sitting out for at least a few hours. It's in order to give the chemicals which are added to tap water a chance to dissolve into the air. It's better for the plants. I'm hungover so can't remember any real words or terms but it's definitely scientific fact. I must go now and drink a few glasses of water which have been sitting out since last night.
posted by stevedawg at 2:44 AM on September 6, 2015

I spent a lot of my formative years in the American Southwest, and it seemed like there was always a drought, and so we were always trying to conserve water. I live in a damp country now, where water is not a problem, but it still seems really wasteful to me to pour a glass of water down the drain. So I drink whatever water is in my glass, even if it's been sitting out for several hours or all night. It doesn't taste that different to me, and we don't have any pets who would be sticking their paws in it.

Also, I spent a lot of time backpacking in the desert, where sometimes the only water sources were potholes full of brown water and algae, where you'd add a capful of iodine and it wouldn't change the color of the water at all, and where sometimes you'd find small dead water-bug-creatures at the bottom of your bottle. So I think my standards for what counts as disgusting-tasting water are maybe a bit more extreme than some people's.
posted by colfax at 3:07 AM on September 6, 2015 [1 favorite]

I take it fresh from the tap by default. As well as the dust and stuff in the air that gently lands (isn't most of it human dead skin in domestic places?) there's also sometimes the issue of not being sure if it's been used for other purposes or not. Also, taking it fresh from the tap moves new water into the piping, which is always good to do.

On the bottled water front: glass always, plastic only if genuinely needed e.g. dehydrated, or the need to take meds.
posted by Wordshore at 3:29 AM on September 6, 2015

Old water tastes like dogshit. And it's not because I'm used to the chlorine--I don't drink tap water at all here.
posted by Joseph Gurl at 6:21 AM on September 6, 2015

Technically, all water is old. I think you are detecting the loss of aeration which happens after a bit.

Carefully cover a half full container and vigorously shake for 30 seconds before drinking.
posted by mygoditsbob at 7:39 AM on September 6, 2015 [2 favorites]

I drink old water all the time, and in fact leave a trail of half-filled glasses in my wake. I'm told it is one of my less appealing attributes, but hey, any place in my home where I am likely to sit, has a glass of water waiting for me!

There is a taste difference, but I find it less of a difference than water drunk from a plastic cup or glass. (Water left in glass or ceramic mug is 1000x better than water left in a plastic cup)
posted by larthegreat at 10:38 AM on September 6, 2015

I don't like old water either. It tastes flat to me. I often use it to water my plants, they like it.
posted by RichardHenryYarbo at 10:52 AM on September 6, 2015

Nthing "all water is old," because what do you think life is like for water before you pour it out of your tap?

It's in pipes, it's in reservoirs, it's all over the place. Leaving it in a glass for a few hours is literally the least interesting thing that's ever happened to it. Pouring it all out is wasteful; add ice or refrigerate it and drink it.
posted by goblinbox at 5:07 PM on September 6, 2015

Tap water from my area that sits out overnight gets a noticeably stale taste. So I usually won't drink water that has sat out longer than that. Also, my apartment is pretty dusty, so I don't like to let water sit out too long for that reason, either. I also worry about having random glasses of water around that might attract insects or be a hazard if knocked over. So those are all reasons I'd cite for not leaving water out too long. Will it hurt you in general, though? Probably not.
posted by limeonaire at 6:06 PM on September 6, 2015

I won't drink water by choice that's been left sitting out for an hour or so, let alone over night, in an open container. It tastes different to me. (Plus, cats do the same thing. I trust them more then dogs, who will drink anything.) A closed container gets a couple of days, but still not too awful long.

As for waste, well, there's almost always a plant to water, and that's what we do when the cat water needs refreshed, and I do the same with mine. Even just tossing it on the lawn is better than the sink. (Pretty sure that habit has kept a couple of plants alive this summer.)
posted by stormyteal at 6:35 PM on September 6, 2015

Agree that all water is old, and just water. (I'm siding with the OP's girlfriend.) Many of the comments here are baffling: a carbonated drink goes flat after a while, meaning its CO₂ is all gone, but how can tap water go flat? I posted a similar question a long time ago, although it concerned bottled, not tap water: Why discard water you've paid for?
posted by Rash at 7:33 PM on September 6, 2015

how can tap water go flat

Because running it through the tap and the air into the glass actually does aerate it, like decanting wine aerates wine. It means that tiny, fine air bubbles are distributed throughout the water in the glass. The taste does change when you pour water through air, and then changes again when that trapped air eventually is forced out of the solution, after it sits for a time.
posted by Miko at 8:03 PM on September 6, 2015

My two things, one of which seems to have been counteracted here is old bottled water, or old water in a plastic cup.

Plastic cup water, especially if it's a softer plastic(like a yoghurt container or disposable water bottle) tends to get noticeable sour, almost citrusy in a gross way. Bottled water, like in a metal water bottle, will start to noticeably smell moldy and gross even if it was a freshly washed bottle beforehand with steaming hot water. I've washed my water bottle with water straight out of a commercial espresso machine after scrubbing it, and sure enough a few days later even if i never drank from the thing it'll start to smell weird.

In a glass cup though? Unless yea, that shit is basically good forever. I used to habitually keep a huge frat house style novelty giant beer glass next to my bed full of water. I'd just top it off, and occasionally scrub the rim or rinse it out. It tasted just as good after sitting for two days as it did when freshly filled.

I think the makeup of the water, and the material of the container(especially if it's sealed but home filled) make a big difference here. Drank from + sealed seems to produce the grossest water the most quickly, but a glass cup keeps indefinitely within reasonable limits.
posted by emptythought at 2:42 AM on September 7, 2015 [1 favorite]

Data point: I drink the vast majority of tap water in my apartment out of glass cups. It still develops a stale taste overnight—actually more chemical-tasting than before. Since leaving out water overnight is one way you can treat it for use in a fish tank (since much of the chlorine evaporates), I'm guessing water in my area must be treated with chloramine, which doesn't evaporate like that. So when some of the water evaporates, perhaps the chloramine becomes more concentrated, along with anything else in the water (and yeah, I usually do make sure to run the tap for 20 seconds before drinking any of the water, but I also live in 100-year-old building, so who knows if that's actually enough to clear the water?).
posted by limeonaire at 5:06 PM on September 7, 2015