There are several reasons.

1. The water in the water dispenser is usually distilled water (purified water), which is obtained by collecting water vapor. It basically contains no minerals (calcium, magnesium, zinc ...), so it can be said that it is only (H2O).

2. It is not good to filter water, because tap water is generally disinfected by chlorine bleaching, and most tap water contains residual components (chloride ions). When water containing chloride ions is left standing for a long time, it will form chlorine gas that is harmful (though harmless) to the body. And tap water must contain n kinds of microorganisms (both harmful and beneficial), and the filter can't filter bacteria.

3. Mineral water, commonly called mineral water, is just a mountain stream somewhere, if it is polluted. result ..............

4. The biggest problem of water and mineral water in drinking fountains is the storage time. When filling and packaging, bacteria will inevitably be mixed, so the bacteria inside will multiply in large numbers. Were you drinking water?

Therefore, I suggest drinking tap water and boiled water that meet the hygiene standards.

But pay attention to a few points.

1. The boiling time should not be too long. If the time is too long, the hardness of water will increase (calcium, magnesium, etc.). Will increase), which is not conducive to health. Not too short. Some bacteria have strong heat resistance and need to be cooked for a long time, basically 3-6 minutes (more than 3 liters) after boiling.

You can't use well water, it's too bad to drink.

How do you know whether the hardness of water is so high? It's very simple. See if there is scale on the back wall of the container where water is boiled for a period of time (usually carbonate sediment, which can be easily washed off with vinegar).

This is my personal understanding, I hope I can help you.