Why does bottled water expire but well/tap water doesn't?

In our impression, water has always existed on the earth. It is an indispensable resource for the survival of all life, including human beings, and is also the most important component of organisms.

Water has existed for so long and has always been full of vitality. For example, we use tap water and well water in our daily lives (when we were young, we drank well water directly). However, why do all kinds of bottled water in supermarkets have expiration dates? Are these waters different? Why is there an expiration date? Let's talk about it today.

01. Why does water expire?

In fact, it is not the water that expires, water will never expire, but other ingredients that enter the water. It is very simple to say, water is water, it is H2O, this extremely simple molecule, and it is very stable.

However, when we say expiration, we are referring to other ingredients because these ingredients may pose a threat to health.

02. Classification of water

Although water itself has a simple structure, when we talk about water, we don’t just mean H2O. So according to the source of water and other components it contains, it can be divided into many types of water:

There are actually quite a lot of national standards regarding water, and many of the ones mentioned above have national standards.

For example, "Sanitary Standard for Drinking Water" (GB5749-2022)

Drinking Natural Mineral Water (GB 8537-2008)

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03. What ingredients will make water expire?

What other ingredients in water affect its shelf life? Let's just pick a bottle of water, which is relatively simple.

Here we can see that our requirements for water are not just H2O, but also a series of other components...

For example, physical and chemical indicators. These indicators are mainly caused by various physical and chemical substances in water.

The physical and chemical properties of these substances will change over time, causing the water quality to become substandard.

For example, chlorine is the basic component of many salts on the one hand, and on the other hand, it is also a commonly used disinfectant. I believe many people know the existence of this substance from the pungent smell in the tap water at home. Sometimes, fish must be exposed to the sun to allow the chlorine to evaporate to avoid harming the fish.

This substance can be partially dissolved in water, but it will evaporate over time. If you put it in a bottle, the structure of the bottle itself may also be affected by chlorine.

As time goes by, it may not be so safe.

For example, microorganisms

The national standard stipulates ingredients such as Escherichia coli and Pseudomonas aeruginosa.

Although these ingredients cannot survive in pure water, you cannot be sure that the water does not contain trace amounts of organic matter, etc. Then there is a possibility that they may multiply over time, posing a risk to health.

In addition, there is the bottle for bottled water, which is commonly made of polyethylene terephthalate plastic, or PET, which is not permanently stable either.

Now you understand that water will never expire, which is why water has existed for so many years and still remains vibrant. The reason why bottled water has a shelf life is because microorganisms and other components enter the water, causing the water to deteriorate, thus posing a risk to health.