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How
Does Reverse Osmosis
Work?
Osmosis is the
phenomenon of water flow
through a semi-permeable
membrane that blocks the
transport of salts or
other solutes through
it. Osmosis is a
fundamental effect in
all-biological systems.
Osmosis is applied to
water purification and
other chemical
laboratory and
industrial processes.
When two water volumes
are separated by a
semi-permeable membrane,
water will flow from the
side of low solute
concentration to the
side of high solute
concentration. The flow
may be stopped or even
reversed by applying
external pressure on the
side of higher
concentration. This is
called reverse osmosis.
(R.O.) Reverse osmosis
is only one stage of a
typical R.O. system.
Sediment and carbon
filtration is normally
included with an R.O.
system, with each stage
of filtration
contributing to the
purification process.
- The first stage
of filtration is the
sediment filter,
which reduces
suspended particles
such as dirt, dust,
and rust.
- The second stage
of filtration is the
carbon filter, or
filters which reduce
volatile organic
chemicals, chlorine,
and other taste and
odor causing
compounds.
- The heart of
Reverse Osmosis is
the membrane. It is
responsible for
rejecting up to 98%
of the total
dissolved solids in
the water. This is
where the
purification takes
place.
What
Is Meant By Total
Dissolved Solids?
In the natural cycle of
water, water that began
its life as rain and
eventually found its way
to your tap has come in
contact with many
sources of potential
contaminant. The various
minerals and salts that
have been dissolved by
the water during this
cycle are called Total
Dissolved Solids (TDS).
What
Type Of Mineral
Contaminants Are Removed
By R.O.?
Reduction of mineral
components that make up
total dissolved solids
will vary up to a
maximum of 99.8%
depending on water
chemistry and pressure.
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Contaminants
|
Average
Influent
Concentration
(mg/L)
|
Average
Effluent
Concentration
(mg/L)
|
Average
Percent
Reduction
|
Maximum
Effluent
Concentration
(mg/L)
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Arsenic
|
0.28
|
0.0035
|
98.7
|
0.0052
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Barium
|
10.2
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0.207
|
97.9
|
0.3
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Cadmium
|
0.036
|
0.0005
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98.6
|
0.0007
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Chromium (Hexavalent)
|
0.15
|
0.013
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91.3
|
0.03
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Chromium
(Trivalent)
|
0.17
|
0.01
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94.1
|
0.01
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Copper
|
3.1
|
0.03
|
99.0
|
0.04
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Cysts
|
149357 #/ml
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5 #/ml
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99.99
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17 #/ml
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Turbidity
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10.2
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0.26
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97.5
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0.83
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Fluoride
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8.0
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0.5
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93.9
|
0.7
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Lead
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0.15
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0.002
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98.6
|
0.003
|
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Perchlorate |
0.10
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0.003
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96.5
|
0.005
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Radium 226/228
|
25 pCi/l
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5 pCi/l
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80.0
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5 pCi/l
|
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Selenium |
0.10
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0.10
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92
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0.011
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TDS |
790
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24
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97
|
800
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The
Reverse Osmosis (RO)
incorporates three
different types of
filtration technology in
order to provide the
best quality water to
the user. The first
stage is a sediment
filter which removes
larger particles and
sediment from your
water. The second and
third stage with in our
RO is our carbon block
filter. We
use only high quality
independently certified
carbon blocks. This
additional certification
on our carbon blocks
ensures the consistency
and integrity of the
carbon block in each
system we sell. These
carbon blocks are able
to reduce many
contaminants with in
your drinking water. The
work horse of our
system, the RO membrane,
is next and is where the
main filtration takes
place to reduce any
remaining contaminates
or up to 97.9% of
impurities in the water.
The RO membrane is
responsible for reducing
many of the difficult
water contaminants such
as arsenic, chromium,
radium and total
dissolved solids. The
fifth and final stage is
a granular activated
carbon filter which
polishes your drinking
water just prior to you
drinking it. The
combination of these
technologies, mainly
with the use of the RO
membrane, is how the RO
system can provide to
you water that is
bottled water quality.
Contaminate
comparison chart for
Reverse Osmosis to
Faucet Mount/Pitchers.
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Contaminates
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Reverse
Osmosis
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Standard
Filtration
Products
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Faucet
Mount and
Pitchers
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Arsenic (Pentavalent)<=300
ppb Reduction* |
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|
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Perchlorate |
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|
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Barium Reduction |
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Cadmium
Reduction
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|
|
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Copper Reduction |
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|
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Cyst Reduction
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|
|
(Faucet)
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Chromium (Hexavalent)
Reduction
|
|
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Fluoride
Reduction
|
|
|
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Lead Reduction
|
|
|
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Radium 226/228
Reduction
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|
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Selenium
Reduction
|
|
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TDS Reduction
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|
|
|
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Chromium
(Trivalent)
Reduction |
|
|
|
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Turbidity
Reduction |
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Chlorine (taste
and odor only)
|
 |
 |
 |
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Results
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15 Reductions
out of 15 |
4 Reductions out
of 15 |
4 Reductions out
of 15 |
Does
R.O. Remove Parasites
Such As Bacteria, Cysts
Or Cryptosporidium?
While a health claim can
not be made because of
intangibles such as
regular maintenance,
these items are too
large to pass through
the TFM membrane. NSF's
rating for reduction of
Giardia Cysts and
Cryptosporidium is 1
micron, and the TFM
membrane filters down to
1/10,000th of a micron.
That is 10,000 times
smaller than these
parasites.
What's The Difference
Between A CTA And TFM
Membrane?
A CTA (Cellulose
Triacetate) membrane is
a paper by-product
membrane bonded to a
synthetic layer. Due to
its cellulose
composition, a CTA
membrane requires
chlorine in the water
source to keep bacteria
from forming on it. A
CTA membrane has a
rejection rate of
between 85-94%. CTA
membranes have an
average life expectancy
of 18-24 months and are
considered inferior to
TFM membranes.
only uses TFM (Thin Film
Membrane) membranes,
which are made of a
synthetic material. A
TFM membrane requires
the chlorine be removed
prior to the water
entering the membrane. A
TFM membrane has a
rejection percentage
between 95-98%, which is
much higher than the CTA
membrane. A TFM membrane
will last between 2-5
years. Many hospitals
use TFM membranes in
their hemo-dialysis
(kidney) machines
because of the higher
purity water they
produce.
What
Happens To The
Impurities That Were In
The Water?
They are washed down the
drain. Unlike filters,
the R.O. membrane is
self-cleaning. As the
source water flows
through the module, it
is divided into two
streams. One stream is
forced through the
membrane by osmotic
pressure created due to
the water pressure on
each side of the
semi-permeable membrane.
The second stream
carries the rejected
salts, dissolved
pollutants and
contaminates to the
drain. Therefore, there
is a minimum
accumulation of debris
on the pressure side of
the membrane. Charcoal
or carbon filters, on
the other hand, become
less efficient with each
glass of water drawn
through them. Carbon
filters only remove a
limited number of
contaminants, some
odors, and some tastes.
Isn't
Water Wasted Down The
Drain With R.O. Systems?
There is a certain
percentage of water from
the system that goes to
the drain. This water is
carrying away the
impurities. These
particles are too small
to be caught by the
filters.
has an
automatic shut-off valve
that shuts off the flow
of water to the drain
when the holding tank is
full. This valve stops
the R.O. system from
continuously running
water down the drain,
thus conserving water
via the R.O. system
working only according
to usage.
What
Is The Ratio Of
Wastewater To The Pure
Water Produced By A
R.O. Unit?
The typical ratio is
4 to 1, based on
incoming water
temperature and
pressure.
Can
This Water Be Saved And
Used?
Yes. Most wastewater
today is recycled for
golf courses and
artificial lakes. The
drain water is slightly
higher in TDS
concentration than the
incoming water, but as
R.O. does not add
anything to the water,
it can be used to water
your lawn or garden.
What
Is The Importance Of
Water Pressure To An
R.O. System?
It is the pressure
of water that forces the
water through the
membrane for
purification and flushes
the rejected solids
away. Low water pressure
will result in reduced
production and premature
fouling of the membrane.
The ideal pressure for
operating an R.O. system
is 60 PSI. Pressure
below 40 PSI is
generally considered
insufficient, and should
be boosted using a
pressure booster pump.
Will
Iron Hurt An R.O.?
Yes. Iron will plug
a R.O. membrane, as the
membrane is not able to
flush iron out. Trace
amounts of iron (up to 2
PPM) can be removed by a
water softener. If the
water contains 1 PPM or
less, there is no need
for concern as the
membrane will usually
last 1-2 years. Note:
This refers to clear
water iron, not red
iron. The difference is
that clear water iron
leaves no visible signs,
whereas red iron leaves
a reddish brown
discoloration in toilet
bowls, tanks, sinks and
tubs. If red iron is
present, steps to remove
the iron will have to be
taken, otherwise the
warranty will be void.
Is
It Necessary To Change
The Filters In The R.O. System
Every Six Months?
Yes. It is highly
recommended. The
R.O. system has been
designed to operate best
to give high quality
purified water with
normal routine
maintenance. By changing
the pre-filters on a
regular six-month basis,
you will eliminate dirt
and chemicals in the
water that will plug the
membrane. After six
months of use, the
carbon filters can have
bacteria growing within
the filter media. Your
local water conditions
may necessitate more
frequent filter changes.
Does
The R.O. Unit Have To Be
Mounted Under The
Kitchen Sink?
No. The R.O. system can
be mounted in a cabinet
to either side of the
kitchen sink or even
mounted remotely in a
garage or basement.
What
Are The Dimensions Of
The R.O. System?
The module part of the
R.O. system measures: 15 ¾" Tall x 16
¼" Wide x 5 ¼" Deep . The
storage tank measures:
11" Diameter x 16" Tall.
How
Far Can A Line Be Run
From The R.O. Unit?
Approximately 20-25 feet
with ¼" POLY tubing. For
runs longer than that,
use 3/8" POLY tubing.
Tubing that runs from
the R.O. system to the
icemaker should always
be POLY tubing, not
copper.
Why
Not Use Copper Tubing
For The Line To The
Icemaker?
Due to R.O. water being
very pure, it is what is
known as "hungry water."
R.O. water can leach the
minerals out of the
copper tubing and may
cause a metallic taste
in the ice cubes and
over a period of time,
the copper tubing can
develop pinhole leaks.
How
Will I Know The R.O. Is
Removing The Dissolved
Solids From The Tap
Water?
You will be able to tell
by the taste and clarity
of the water. For
example, ice cubes made
with the R.O. water are
harder, clearer, and
last much longer. If you
take two clean glasses
of the same size and put
ice cubes made with R.O.
water in one and the
same number of ice cubes
made from tap water in
the other, you will
notice that it takes
longer for the R.O. ice
cubes to melt. Not only
do ice cubes made with
R.O. water last longer
but juices and mixed
drinks made with R.O.
water taste better. When
ice cubes made from tap
water are melted in a
glass, you will most
likely see unsightly
sediments on the bottom.
This is not so with R.O.
water. Another way of
determining the amount
of dissolved solids
removed from tap water
is by the use of a
conductivity meter. This
meter measures the
conductivity the
dissolved solids impart
to the water. This is
converted on the meter
scale into parts per
million of Total
Dissolved Solids (TDS).
offers a water
sample kit for the
testing of a customer's
water to determine how
the TFM membrane is
working and when to
replace the membrane.
Will
An R.O. Soften Water?
Yes. R.O. water is
softened through the
reverse osmosis
purification process;
however hard water
(above 7 grains of
hardness) will shorten
the life of the
membrane. The harder the
water, the shorter the
life. Example: If you
incoming water is 15
grains hard, you may
only get 2-3 years of
life from your membrane.
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