"Gill Passman" wrote in message
...
BoyPete wrote:


Just why would tap water be saline? It's 'fresh' water.

LOL - I've been dying to ask that question every since I saw the question
of salinity raised in this thread......and BTW I do have a hydrometer and
have checked the tap water (zero of course) but only out of idle
curiousity after checking my marine tanks....

Gill

I have been told the hydrometers just aren't sensitive enough to be able to
measure the salinity of tap water or even our pond water. They are designed
for testing water with salinity of around 3.5%. My pond water tests at
around 0.03 or 0.04% by salinity meter without any salt additions. When
treating for nitrites, the level desired is around 0.1% to 0.15% which is
still a very low level compared to the design of the hydrometer.

One of the bottled waters that we have bought for drinking is a product of
reverse osmosis or distillation, per the bottle, with sodium chloride and
calcium carbonate added for flavor. G