The term "fresh water" usually refers to water that isn't salty, to
distinguish it from ocean water. I have no idea why they chose that
term, as some "fresh water" probably wouldn't pass any freshness test,
such as what flows out of many rivers, which is full of silt and
pollutants, but somehow is still called "fresh water".
Tap water in the United States is usually purified and
disinfected. It may contain fluoride, chlorine, and other additives. It
counts as fresh water in that it is much less salty than ocean water,
but there are usually some dissolved salts in tap water. Calcium
carbonate is a dissolved salt in many tap waters which makes the water
"hard" (soaps don't work so well when there's a lot of calcium
carbonate, and calcium carbonate deposits clog up teakettles and
pipes). One solution to this is for a wter softener to exchange calcium
carbonate salt for sodium chloride salt. The concentrations are still
so low that the treated tap water can still be called "fresh".
Tom
(published on 10/22/2007)
