It has happened to all of us at some point: we buy a bottle of water, open it and leave it on the counter or on the nightstand all weekend, or even inside our backpack for several days. Although the expiration or best-before date helps us determine whether we can drink from that bottle or not, what happens when we have already opened it? Does it last the same as if we don’t open it? How long can we keep it open?
Whatever the case, day-old water is not at the top of the list of public health concerns, as it is very unlikely to cause any illnesses, although it may not taste very good, especially if it has not been covered. But the more time you spend inside, the more likely problems are to appear.
Does bottled water go bad after opening?
Although a closed water bottle can be safely drunk even after years, once opened its useful life is drastically shortened, as it is exposed to air and possible contaminants that come from our own hands and even our mouths. When the water remains in the bottle for several days, it is possible that a breeding ground is formed where mold spores from the hands live and end up in the liquid.
If we also leave it at room temperature, bacteria can begin to grow inside the bottle after a few days, especially if we drink directly from the bottle.
In this case, we must keep in mind that with every sip we take, new bacteria can be introduced, most of them coming from our mouth, which has its own microbiome. But it is unlikely that our own bacteria cause us any illness. However, if we share that bottle with other people, other types of bacteria can be introduced, which increases the risk of exposing ourselves.
Also your hands, if they are dirty, play a determining role, since it is easy to grab the edge of the cap with your hands. unwashed hands and bacteria appear like E.coli, Salmonella and Staphylococcus aureus.
The risk increases when the water we drink is exposed to heat—such as the temperatures reached inside a car on a sunny day—because heat accelerates the growth of bacteria. Also if we leave the bottle open for a few hours: in this case the water can accumulate dust, debris and other small particles from the air. Although this is unlikely to cause harm, it can alter the taste of the water if we drink it the next day.
Another point that we must take into account is the origin of the water. If we have filled the bottle with tap water, which contains chlorine to kill bacteria, parasites and viruses, it is essential to remember that this dissipates when exposed to air and can almost completely disappear after one to five days. Depending on how long the water has been out, it may have lost this bacterial defense.
Therefore, an opened bottle of water should be consumed as soon as possible if we want to obtain maximum freshness and purity. In addition, it is preferable, whenever we can, to store it in the refrigerator to stop bacterial growth.
Glass or plastic
The containers and material in which the water is stored also influence the maintenance of the properties of the water.
Although time is not usually an issue when it comes to bottled water safety, there are other factors that can be. One of them is the temperature, especially when we talk about plastic bottles. And as storage temperatures increase, so do the risks. At least this is what a study published in ScienceDirect according to which plastic water bottles stored at 65°C show antimony levels higher than the limits established by the Food and Drug Administration (the US FDA) after 38 days.
Prolonged exposure to heat and sun can also cause mold and algae to appear, which suggests storing it in a cool, dark place, in a pantry or basement away from sunlight. And this works for both the plastic and glass bottles.
Glass bottles, on the other hand, have certain advantages over plastic bottles, since it is a more hygienic material. In this case, there is no risk of inorganic chemicals leaching into the liquid when it is heated or cooled. In addition, it does not rust and withstands numerous washings and sterilizations. Glass water bottles are non-porous, meaning they do not absorb flavors or odors from the liquids they contain. They are also durable and easy to clean although they can break easily.
Tips to keep bottle water clean
We don’t usually treat water bottles like we do other kitchen utensils like glasses. Once we have drunk, we put it aside until we use it again, or we refill it, while an empty glass ends up safely in the dishwasher or, at the very least, we rinse it. What can we do so that the water bottle does not fill with germs over time?
- Keep the water covered to protect the water from potentially harmful bacteria and avoid leaving the bottle with water in it for long periods of time between uses.
- If the water has been in the bottle for many days, we can use it to water the plants.
- Avoid drinking water from a bottle that has been in a car in the sun.
- Store single-use plastic water bottles in a cool, dark place and respect the best-before dates.
- Avoid sharing the water bottle with another person.
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