Distilled water is 100% pure H[sub]2[/sub]O, having been evaporated and then condensed in a still. Only the very rare solutes with a lower boiling point than 212 degrees would “contaminate” it.
Tap water, well water, spring water, etc., is almost-pure water, but nearly always has something dissolved in it owing to water’s properties as a near-universal solvent for any polar molecule. (Oils, fats, etc., are non-polar; almost every inorganic molecule or crystal, and many organic molecules, are polar.) If you live in a limestone or dolostone area, there’s dissolved CaCO[sub]2[/sub]; in a red-clay area, various clay-forming stuff including iron oxide; sulphates dissolve easily; etc. A municipal water system will attempt to combat microbial contamination by adding chlorine; many places fluoridate their water; some use alum to neutralize the pH value.
“Purified” water, whether through a tap attachment or from commercial purposes, is water that has been run through activated charcoal and other filtration methods to remove the majority of solutes. But none are completely successful.
Actually, with the advent of decent membranes over the last 20 years, reverse osmosis systems are getting pretty good. RO water is widely used in the pharmaceutical industry.
My ENT said I could use tap water with table salt to do sinus rinses and it would be fine. I have been doing that and it works just as well as with distilled water.
I mistakenly bought distilled water, I could barely drink it, it tates horrible. I guess there is some sort of salts or other minerals in regular water that add to the taste.Never realized that before.