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gulp! is it bad to drink old water?

we have all taken a swig of water that has been sitting in a glass or bottle for a couple of days, but we could be swallowing more than just h₂o.

by nick beare

mar 30 2022

3 minute read

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if you have ever taken a sip of water that's been sitting in a glass or bottle all night, you know that sometimes it can taste a little different. getty

in an effort to stay properly hydrated and hit that elusive four-to-six cups of water per day mark, i will often bring a glass of water to bed. sometimes i finish the water before falling asleep, other times i wake up with a full glass still on the night table.

depending on how rushed i am in the morning and how tired i am that night, there’s a good chance that i will be sipping that same water — perhaps for a day or two. is that bad?

what happens to water that sits overnight?

if you have ever taken a sip of water that’s been sitting in a glass or bottle all night, you know that sometimes it can taste a little different. that’s because the chemistry of water changes over time. but it’s not like it goes bad.

water doesn’t have any sugars or proteins in it, so there aren’t any microbes in there that can cause it to rot. however, water does absorb some co2 which lowers the ph levels and makes the water a little more acidic, according to discovery news . that little bit of acidity changes the taste.

and there’s the extras that your mouth adds. if you take a few swigs of water before you fall asleep, you are adding a bunch of tiny microorganisms to the water that will start to multiply quickly — no matter how well you brushed your teeth. and although most bottled and tap water has chlorine additives that will kill off those microorganisms, the chlorine will evaporate overnight if left in an open container — like a glass — leaving the microorganisms to multiply.

also, dust and other debris — maybe a fly? — can land in the water, leading to bacteria growth — especially if the water is left in the open for an extended period. water left outside is a different story altogether, as algae can start to grow on the surface. standing water outside also makes the perfect host for mosquito larvae, so, definitely don’t drink that.

can you get sick from drinking old water?

as the director of the johns hopkins university water institute, dr. kellogg schwab, told time in an interview, “if you have clean water in a clean glass, you’re fine for a day or two.”

there are things, however, that increase the likelihood of getting sick from the water that sits by your bed, like sharing your glass. introducing your own microorganisms to the clear liquid is one thing, but if someone else has put their mouth or fingers on the glass, especially if that person recently came from the bathroom, there’s a chance the water could be contaminated. touching the water with your own dirty hands is also a no-no, of course.

still, the chances of getting sick from “old’ water is low — as schwab put it: “this is far from the top of the list of public health concerns.”

ditch the open glass to keep water fresh

does a plastic water bottle instead of a glass make a difference?

while keeping the cap on a bottle of water will prevent dust and debris from settling in your water, a plastic bottle which is not meant for reuse can still present a problem. the plastic is not impermeable, so leaving the bottle exposed to heat or direct sunlight can cause a hormone disruptor called bisphenol-a, or bpa, to leach into the water.

your best bet is to use a metal, glass or bpa-free plastic container with a lid to store your water overnight.

a lid can also be handy if you’re the type to flail your arms in the night or knock things over while blindly reaching for your phone. trust me.

nick beare is a toronto-based writer.

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gulp! is it bad to drink old water?

we have all taken a swig of water that has been sitting in a glass or bottle for a couple of days, but we could be swallowing more than just h₂o.

what happens to water that sits overnight?

watch: we're not fans of the extra-bitter #lemoncoffee trend

study finds that the messages on food packages influence our taste

can you get sick from drinking old water?

ditch the open glass to keep water fresh

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gulp! is it bad to drink old water?

we have all taken a swig of water that has been sitting in a glass or bottle for a couple of days, but we could be swallowing more than just h₂o.

what happens to water that sits overnight?

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can you get sick from drinking old water?

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