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Subject: Water purification

Water purification

From: Jim Druzik <jdruzik>
Date: Friday, November 11, 1994
    **** Moderator's comments: In response to Jim's previous message, I
    asked him about the term "ultrapure".  For background, one way of
    measuring the purity of water is by its electrical resistivity
    (measured in megohms): the purer the water (the lower the ionic
    concentration), the harder it is to push an electrical current
    through it. Our lab's DI system produces 10 megohm water (before
    recalcification), but some systems (used, among other things, for
    biotech and semiconductor applications) can deliver 100 megohm
    water. Here is Jim's reply

I was actually referring to anything like distilled or triple distilled
or produced from your own still.  Actually it is the latter I'm most
addressing.  When the architect said distilled water "on tap" was
expensive he was probably quoting an installed high volume still which
we rejected ourselves.  Distilled vs DI supermarket bottled water is
just not that big a difference to worry over.

The water we use is not rated physically (like you mentioned) but rather
in chemical purity terms like maximum UV absorbance or fluorescence at
such-and-such wavelength or a maximum TDS of less that 2 ppm.

Reverse osmosis is just fine.  I've used reverse osmosis water through a
single Dahlia Sprayer for 14 years without any signs of a problem--no
maintenance, no cleaning, not no nothin'.  Since this is just to relax
paper I'm not too concerned about stripping out protective cations.

If one wanted to be extra cautious, you can always get those little La
Motte (spelling?) test kits and monitor for copper, iron, chlorides,
etc. just to double check on the system.  One added word of caution from
a Californian.  Reverse osmosis water is not going to give you safe
water after an earthquake if the water system has been compromised (this
is the word from Culligan.)  Viruses still seem to be able to get past
them.  Culligan may be saying that to save themselves from litigation
because I picked up a virus-filtering system at a local camping
outfitter for 60 bucks which doesn't seem any higher technology than the
DI system I purchased.  I bet Culligan is really saying that it's
hardware installations across the board will have ways viruses can get
around them rather than the filters aren't good for such small submicron
particles.  But maybe I'm wrong.

Also people don't generally know that reverse osmosis is terribly
wasteful on your essential water supply.  So if you are
hyper-environmentalistic, from Santa Barbara or Saudi Arabia, it's best
to buy water during serious droughts.


                  Conservation DistList Instance 8:37
                 Distributed: Sunday, November 13, 1994
                        Message Id: cdl-8-37-007
Received on Friday, 11 November, 1994

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