How long does it take for a glass of water to go bad?

August 25, 2023

Have you ever noticed that your water tastes funny after that’s been standing on your bedside table all night? No, your water hasn’t gone bad and it won’t make you sick either. Your taste buds also aren’t playing tricks on you, they’re actually quite accurate at detecting subtle changes in flavour.

Water is vital to our health, as it enables our bodies to function at their peak. Staying hydrated will not only ensure a happy, healthy body but also support organ functioning, cell regeneration, and sleep. Hangovers are an unpleasant example of what dehydration does to our brain and body.

Needless to say, your body needs H2O throughout the day, so drinking your daily quota all at once in the morning or at night is not greatly effective. That being said, most of us go to bed with a glass of water on the nightstand to sip on should we get thirsty in the middle of the night. However, by the time we wake up, all bleary-eyed and dry-mouthed, that glass of H20 tastes stale and off. There’s a natural and scientific explanation behind this phenomenon.

Can Water Go Bad

When water is exposed to open air for a couple of hours, the interaction between carbon dioxide in the air and the liquid in the glass changes its chemical composition. This interaction lowers the water’s PH to a more acidic level, which results in an off taste. Even though this change is slight, it’s enough for your tongue to detect the difference.

After extensive research into different facts and opinions, the scientific route seems more trustworthy than Joe Soap down at the pub. According to Truls Krogh, director of the Department of Water Hygiene at the Norwegian Institute of Public Health, “if the water is covered and of good quality to start with, in principle it can last a thousand years”. This means the water must be free from contaminants to begin with and sealed in a container that doesn’t let any impurities enter.

According to Krogh, even an open glass of water that has been standing out for a number of days is safe to drink, provided it hasn’t been contaminated with bacteria from dirty hands or saliva. It may taste flat and odd, but it is still safe to consume.

However, on the side of caution, we wouldn’t recommend drinking “old” water, unless it’s an emergency of course.

Is Bottled Water Better than Tap Water?

Whilst tap water in the UK is considered safe to drink, and is subject to extensive water treatment, bottled water is considered purer, and some tests show that there is less bacteria in bottled water.

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This article was originally featured on The Water Delivery Company blog.

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