Olly's original premise and some of the comments above are apparently
based on RO systems used to purify household water. Marine seawater RO
systems -- watermakers -- work in the same way, but because they start
with seawater, they end up at a very different point.

Seawater is a little above 30,000ppm total dissolved solids (TDS).
Watermakers typically are designed for rejection rates between 99.2
and 99.5%, which results in product water at around 200ppm TDS. Since
the FDA recommends that potable water have TDS below 500ppm, why make
the unit work harder than is necessary, with some room to spare?

This is by no means on the low side of healthy. If anything for
people with sodium problems, it's probably high. The three upper Great
Lakes run at around 170ppm, and millions of people drink that water
without problems.

Now, if you run domestic tap water through an RO that is designed to
produce very low TDS, you can get the TDS way down to the point of
unhealthy, but that's not an option or problem that any of us have at
sea.


Jim Woodward
www.mvFintry.com

Glenn Ashmore wrote in message news:5uRlb.90609$sp2.10288@lakeread04...
verly paranoid. Virtually all of the health nut web sites recommend RO
water. RO systems are not perfect and do take at least a minimum amount
of care but they are WAY better than most shore supplies. Desalinating
RO systems are not intended as purifiers. Purification is a by product
of desalination. It does reject most bacteria but not most viruses so UV
post treatment is a good idea as is a regularly maintained carbon
filter. With proper flushing with fresh product water the bacterial
buildup is minimal and the toxins released will be at a level in PPM
lower than any health standards.

The primary essential minerals removed by RO are sodium, magnesium and
potassium. But the depletion rate in body tissue is slow and easy to
replentish. A normal healthy diet will supply all you need. Use
iodized salt on your eggs and take an occasional shot of Kaopektate if
you are worried about it. Makes you a regular fella to boot! :-)

Chemically pure water is less biologically active. This works to an
advantage if used to flush the membranes because bacterial growth will
be slowed. There is a school of thought however that claims a severe
lack of biologically active water may be harmful to the body but eating
Fresh fruit and vegatables will supply plenty of it. What hurts the
credibility of this idea for me is that this same school claims that
magnets and crystals can restore the activity.

RichH wrote:

RO water used for drinking will definitely harm you long term.
RO water has most of the ionic molecules removed.
The laws of Chemical equilibrium will cause these missing ions (some are
essential) to be removed from your body, thus causing a long term
deficit. Consult with you Primary Health Care Provider and work out a
regimin for replacment of these chemicals.
Larry should get a NEW physician! .... its not whats in the water; but,
what such water REMOVES from you.

RO doesnt remove *all* the bacteria from water. RO membranes are not
that efficient, nor precisely made. What Larry states is a common
problem with poorly maintained or poorly designed RO systems: when the
'dead' bacteria that are trapped on the membrane decompose, the cell
contents mix with the effluent water. Some of these decomposition
products (endotoxins) are toxic and are FEVER producers. The worse the
system maintenance the greater potential to get sick; and it takes an
'expert' to maintain properly. An RO machine that is not running
*flat-out* 100% of the time is a brewery for bacteria.
Thats why I dont have filters or RO machines on my boat's water system
.... and Im deeply involved in filtration/membranes/RO, etc.