RO is basically a filter with very small pores and water is forced
under pressure. It's a slow system, producing filtered water gradually
storing it in a tank. Here are the problems.
1) The filter material, which has _very_ small pores, allowing through
those molecules of atomic weight less that about 180 (water is 18), is
in a high tech process. There are two kinds, "Thin Film Composite"
and "Cellulose Acetate"/"Cellulose Tri-Acetate" (CA/CTA). The second
preferable on a techinical basis because it is not as easily degraded
chlorine as the first. Problem is that the process necessary to make
thing involves the use of some nasty chemicals:
[From Lono Kahuna upua A'O's book "Don't Drink the Water", second
ed. 1998, ISBN 0-9628882-9-x]
A major question about RO systems using CA or CTA membranes
surfaced through the research of Gene Shaparenko, owner of Aqua
Technology Water Stores, a company which manufactures distillers.
discovered that a chemical, known as 1,4,dioxane, is applied to the
cellulosic materials of which CA or CTA membranes are made.
_The South Valley Times_, article "Lifelines", Apr 1990] Its
to etch the small pores in the material through which the water is
filtered. 1,4 dioxane is a colorless solvent which mixes easily
water. It is known to be extremely toxic when inhaled or absorbed
skin contact. It is ranked alongside asbestos, benzene, carbon
tetrachloride, DDT, formaldehyde, msutard, gas, PCBs, TCE, and
chloride in the State of California's Toxic Chemical List.
According to Mr. Shaparenko, no one at the state or federal level
government seems to know that this chemical has been routinely used
manufacture membranes which are used to "purify" water. Nor does
seem to know just how much of the chemical leaches into the
water product, or how many gallons it takes to effectively purge
chemical, if indeed, it is purged at all.
This is a major concern, because the vast majority of RO systems
residential use have employed CTA membranes. Not only are they
than TFC membranes, but resistant to chlorine, and most residential
customers are on chlorinated water supplies...
He may want to know this. I am not clear what the manufacturing
for the TFC membranes, but they have been around longer and they may
been more closely inspected for their manufacturing methods. If he
to TFC then he will need to put in a prefilter to remove the chlorine
TFC filter does not get degraded.
2) Another quote from the same book:
According to a study published in Canada by Canadian virologists,
Payment, Eduardo Franco, Lesley Richardson, and Jack Siemiatyci,
"Gastrointestinal Health Effects Associated with the Consumption of
Drinking Water Produced by Point-of-use Domestic Reverse osmosis
Filtration Units," "Applied and Environmental Microbiology," Vol.
no. 4, April 1991, pp. 943-948.] it was discovered that RO systems
penchant for growing bacteria, apparently because the finished
devoid of chlorine and it takes so long to be made. Because the
sits stagnant at room temperature, sometimes for days, RO systems
an ideal breeding ground for bacteria, which can double their
every 20 minutes or so. In their study of many types of RO
virologists measured an average of 10,000 bacteria per millileter
water - 20 times the accepted level for city tap water. About a
of filters produced water with more that 100,000 bacteria per ml,
times more than average tap water. Some bred up to 10 million
The study went on to further demonstrate that, because of this
contamination (which occurs because bacteria contaminating the end
dispensing faucet can be "sucked back" into the storage reservoir),
people who drink RO water suffer 10 times the number of bouts of
gastroenteritis as people who drink tap water.
The book's suggestion, if one has an RO system, is to replace CA/CTA
membranes by TFC membranes, put a prefilter like what is known as
get rid of the chlorine, and add an ultra violet unit between the
tank and the water dispensing faucet to kill the bacteria, and he even
suggests a carbon post-filter between the RO unit and the storage
Now, I have not looked into the manufacturing process used to make these
filters, so I don't know that they don't use something nasty too, but the
little I know so far, it seems like it might be ok (it's apparently just
zinc-copper alloy). Also the carbon filters include "Activated",
"Catalytic-Activated" and some of the "Catalytic-Activated" are
silver nitrate to keep bacteria from growing. This latter is also
and to be avoided. I am not clear on the maufacturing process for other
"Catalytic-Activated" filters. Even the merely "Activated" ones are made
some sort of steam process starting from wood, coal or petroleum
Those three get more distasteful as you do down the line. [Added for
Or coconut fibers - probably what we should go for.]
[Also I had a note about the availability of a] small KDF filter for
shower to get rid of the chlorine [29 bucks at HomeFocusCatalog.com, part
number 1181128, 800-624-2112 and supposedly it lasts for a year]. I'm
showering in cold so that I don't inhale the steam which contains all
chlorine byproducts and fluorine (along with a whole list of others that
won't bother with here).
One more point on exposure. The EPA has standard methods to test
exposure to a pollutant in water. Accoring to those standard
calculations, 60% of our exposure comes through drinking the water and a
full 40% comes from a) showering (skin absorption and inhallation of
steam) and b) absorbing the pollutant through the skin which is in
contact with cloths washed in the water. Since I cant figure out how to
get the fluoride out of the water, I have taken the following measures:
1) I get my drinking water from a well tested spring. I use it to
drink, cook and wash my vegetables.
2) I get water from a well that is dependable and which I use to bathe (I
heat it on the stove, like the good old days) and wash my cloths (by
hand, it's not hard).