opened bottle
Can water go bad?
Many people fill up reusable bottles with tap water.
© New Africa/Shutterstock.com
Almost everyone has an opened bottle of water lying around somewhere. Can you still drink this?
Whether next to the bed, on the desk or in the car – most people always have a water bottle lying around somewhere. After all, that’s also important: at least two liters We should drink water every day to be sufficiently hydrated – especially on warm days. But water bottles often remain open for a while. Taking a sip of water from a half-full bottle may seem harmless at first glance. But can water also go bad?
Mineral water: quality has its limits
Basically, mineral water is a strictly monitored foodstuff, freshly opened it can always be drunk without hesitation – even if the bottle has been in a warm place for a long time. However, there is also a best-before date for mineral water. This is required by law in the Mineral and Table Water Ordinance. It is two years in glass bottles and around one year in PET bottles. If mineral water is stored in a cool and dark place – i.e. preferably in the fridge – it can usually be drunk long after the best-before date has passed.
But what about opened bottles? It is well known that water from an open bottle tastes stale after a short time. This is because the chemical composition of the water changes as soon as oxygen gets inside the bottle. As a result, the pH value of the water drops and a sour taste develops. This is not harmful, only the taste is affected.
Nevertheless, from a health point of view, it is advisable to drink open water bottles as quickly as possible. If the bottle is open, microorganisms can get into the bottle. If you drink directly from the bottle with your mouth, bacteria can also get into the bottle through the saliva. Sharing bottles can therefore also be problematic.
Bacteria and germs in tap water
Many people rely on tap water for their hydration – after all, it is of high quality in Germany and more environmentally friendly than bottled water. But what about durability? Theoretically, water is considered non-perishable because it consists only of hydrogen and oxygen and contains no substances such as protein or sugar that could ferment.
When filling from the tap, however, the tap water comes into contact with environmental germs. According to the Federal Center for Nutrition (BzfE) however, that is not a problem. However, factors that can increase the germ load are light, heat and food (e.g. dirty bottles or glasses).
As with mineral water, the shelf life of tap water depends on correct storage. If you fill your water in clean containers and do not expose it to sunlight for long on warm days, you can drink it for a long time with peace of mind. Reusable water bottles should be cleaned regularly in the dishwasher, PET bottles should not be filled more than once. In general, the health risk from germs or bacteria is rather low for healthy people, and the taste of the water suffers the most.