Reader Question – What’s The Difference Between Tap, Distilled and Sterile Water?

Tap water is simply the water that comes out of your faucets when you open them. For many decades, in most industrialized nations the term tap water has been synonymous with the safe drinking water commonly supplied by our municipalities. However, as consumers see an increasing frequency of stories about contaminated drinking water, the faith in our tap water is diminishing.

It is important to know that in many places the tap water is not safe to drink. In Saint Thomas for instance, the tap water comes from untreated cisterns and is used only for non-drinking purposes. It is a blessing for us to have safe, drinkable tap water.

Distilled water is water that is produced by the process of, (you guessed it), distillation. Distillation is a simple process that uses heat to bring water to it’s boiling point (212°F). Water is then converted to steam, the steam rises and is channeled through a cooling tube (condensing tube), the steam is then cooled and finally reforms as distilled water in a new collecting container.

Many believe that distilled water is pure water, but it is not. While it is true that the vast majority of inorganic impurities are left behind in the boiling pot, there still are small amounts of these contaminants in distilled water. Inorganic impurities are things like calcium, magnesium, lead and chromium. For the record, water purification technology can produce water that is 18 times purer than triple distilled water.

Make no mistake however, that distilled water is very pure and it is desirable to use in applications where machines need to be protected from scale deposits. Examples of such machines would be dehumidifiers and CPAP machines.

Where distilled water shines, is in the last part of the question; sterility. Sterile water is defined as having no contamination from microorganisms such as bacteria, algae, viruses, molds and more. The highest standard for sterile water, USP WFI (water for injection), calls for distilled water or equivalent.

Be advised, sterile water does not remain sterile for long. It quickly absorbs contaminants from the surrounding environment, and since it no longer has chlorine in it, sterile water quickly starts to grow microorganisms.


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