When companies (including ourselves) advertise pure water, what they’re usually saying is that the water has been sourced from a natural spring, or may have gone through a filtering process to remove impurities like chemicals and other contaminants.
Pure water doesn’t exist in nature because water is electromagnetic and one of the “stickiest” substances in the universe, which means that it can easily “grab” onto other atoms and dissolve them. This happens with literally anything it comes into contact with—glass, plastic, metal, even air particles. And when you have a substance that sticky, it’s impossible to keep it pure. It would be like running a strip of duct tape along a sandy beach and trying to keep it sand-free, except with water, it grabs particles from everything. That’s why it’s called the “universal solvent.” It grabs the atoms from almost anything it comes into contact with, and then dissolves it. It’s the reason for some of Earth’s most spectacular wonders: the Grand Canyon, Niagara Falls, Ha Long Bay, and so much more.
If scientists wanted to create 100% pure water, they would require a perfect vacuum that didn’t have any other atoms in it. But because the universe is literally made of atoms, it’s impossible to create a perfect vacuum, and therefore impossible to make pure water.
Even if scientists could make 100% pure water, you wouldn’t want to drink it anyway. Regular water can contain lots of minerals that we need for our bodies, including zinc, sodium, potassium, magnesium, iron, calcium, and bicarbonate. If we drank 100% pure water, we wouldn’t be getting any of these benefits. That’s why mineral water can be a healthy choice for many. Traditionally-marketed pure water can also contain lots of these goodies, but has usually been through an additional filtration process to remove any nasty bacteria and other pollutants.
Surprisingly, 100% pure water wouldn’t even work well for manufacturing or delicate scientific processes, because the purer the water, the “stickier” it is and the better it is at dissolving things. So if you put it in a machine, a beaker, or anything else, it would grab the atoms from its container and corrode them. What manufacturers and scientists tend to use is something called ultrapure water (UPW), which is pure enough, but not so pure that it becomes corrosive. This type of water has been through a stringent purification process to remove contaminants such as organic and inorganic compounds, particulate matter, volatile and non-volatile matter, and more.
If you drank 100% pure water, it could even be dangerous for you because as soon as it touches your lips and mouth, it would start to leach important minerals from your saliva, leaving you less healthy than you were before. It’s crucial to note that this isn’t the case for regularly marketed pure water (which is very healthy because it’s so clean). It’s only true for mythic 100% pure water, which is impossible to create anyway.