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Does water from opened bottles go bad or does it just taste bland?

By Carolin Berscheid | April 20, 2021, 12:04 p.m.

Whether at home next to the bed, in the car or on the desk at work - most people always have a water bottle standing around somewhere. That's right, because as we all know, it is important to drink a lot! Often, however, the bottles are stored in said locations for a few days after opening. Should I still drink the water then?

Water can't go bad, can it? FITBOOK explains how long you can drink from an opened water bottle or how long the contents can be kept. Is there a risk of germs and bacteria - and when is it better to dispose of the bottle?

Does water have a best-before date?

Water can't go bad - at least that's what they say. If you take a closer look, however, you will find that a best-before date is also printed on water bottles. This is required by law in the Mineral and Table Water Ordinance. According to this, water in PET bottles should be stable for at least one year, and in glass bottles two years from the time of filling. According to the Information Center for German Mineral Water, there are no concerns about hygienic bottling even after the best-before date. Because of the preserving effect of the carbonic acid, water can be kept almost indefinitely. But what is it like when you've already opened the bottle?

The taste of opened bottles suffers most

First of all, you will probably find that water from an opened bottle tastes rather stale after a very short time. But why is that even so? This is because the chemical composition changes as soon as you open the bottle and oxygen from the air gets inside. Part of the liquid is converted into carbonic acid. As a result, the pH value of the water drops and a sour taste develops. However, this is not harmful, only the taste experience is no longer entirely flawless. Incidentally, this happens particularly quickly with plastic bottles. This is because these are more permeable than glass, which speeds up the process. It is therefore advisable to use the glass bottle better, not only for environmental reasons.

Also interesting: are there dangerous germs in water dispensers?

Germs and pathogens mainly collect on the edge of the bottle

From a health point of view, it is generally advisable to drink the opened water bottle within a few days. When the bottle is opened, so-called microorganisms can get into the bottle, which can multiply quickly over time, especially in a bright and warm environment. If you drink directly from the bottle with your mouth, bacteria can also get into the bottle through the saliva. However, this only becomes a concern if you share your drink with another person. Your own bacteria are generally not harmful to your health, but by drinking together from a bottle pathogens such as cold or herpes viruses can easily be transmitted. These stick especially to the edge of the bottle. It is therefore advisable to drink water from your own, clean glass. But you should also do this quickly, as otherwise germs can form in the water glass and dust, dirt or mold particles can collect.

Also interesting: How do you prevent germs in the drinking bottle?

Store opened water bottles properly

To ensure that water stays fresh for as long as possible, correct storage is particularly important. It is best to keep opened bottles in the refrigerator or other dark, dry, and cool place. In the car, on the windowsill or outside, you shouldn't leave your water bottle lying around, especially on warm summer days.


How long the contents of an opened water bottle can be used also depends on storage. The health risk from germs and bacteria when the bottles are opened is rather low or influenced by other factors. The taste of the water suffers most. If you use up your water quickly and don't leave it in the sun for too long, you shouldn't have any reason to worry.

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