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These are questions
which we have been asked numerous times when helping
our customers select a filters or a water filtration
system which is right for them.
Below you will find diagrams and answers to those
questions. If you have other questions which are not
answered, please visit our FAQ
page or Contact
Us. |
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Click
Here for Pricing and Features
of our best selling Reverse Osmosis Systems. |
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Producing Drinking Water Using Reverse Osmosis
Although Reverse Osmosis seems like a complex
system it is really a simple and straightforward water filtration
process. And it's not a new process. High-pressure (pump
driven) reverse osmosis systems have been used for years
to desalinate* water
– to convert brackish or seawater to drinking water.
Having a better understanding of how a reverse osmosis system
works will eliminate the mystery and confusion you may feel
when you look at a reverse osmosis system -- with its many
colored tubes and multitude of filters. Read on to enhance
your knowledge of residential reverse osmosis systems.
The most important points to remember
- All RO Systems work the same way.
- Most RO (Reverse Osmosis) systems look alike.
- All RO Systems have the same basic components.
- The real difference is the quality of the filters
and membranes inside the RO.
How the Reverse Osmosis System Works
Reverse Osmosis is a process in which dissolved
inorganic solids (such as salts) are removed from a solution
(such as water). This is accomplished by household water
pressure pushing the tap water through a semi permeable
membrane. The membrane (which is about as thick as cellophane)
allows only the water to pass through, not the impurities
or contaminates. These impurities and contaminates are flushed
down the drain.
For a definition of **Osmosis Click
Here.
Ultimately, the factors that affect the performance
of a Reverse Osmosis System are:
Incoming water pressure
Water Temperature
Type and number of total dissolved solids (TDS) in the
tap water
The quality of the filters and membranes used in the RO
System (see operating specs)
What does a Reverse Osmosis System Remove?
A reverse osmosis membrane will remove impurities
and particles larger than .001 microns.
These basic components are common to all
reverse osmosis systems :
- Cold Water Line Valve: Valve
that fits onto the cold water supply line. The valve
has a tube that attaches to the inlet side of the RO
pre filter. This is the water source for the RO system.
- Pre-Filter (s): Water
from the cold water supply line enters the RO pre filter
first. There may be more than one pre-filter used in
a reverse osmosis system. The most commonly used pre-filters
are sediment filters. These are used to remove sand
silt, dirt and other sediment. Additionally, carbon
filters may be used to remove chlorine, which can have
a negative effect on TFC (thin film composite) &
TFM (thin film material) membranes. Carbon pre filters
are not used if the RO system contains a CTA (cellulose
tri-acetate) membrane.
- Reverse Osmosis Membrane: The
reverse osmosis membrane is the heart of the system.
The most commonly used is a spiral wound of which there
are two options: the CTA (cellulose tri-acetate), which
is chlorine tolerant, and the TFC/TFM (thin film composite/material),
which is not chlorine tolerant.
- Post filter (s): After
the water leaves the RO storage tank, but before going
to the RO faucet, the product water goes through the
post filter (s). The post filter (s) is generally carbon
(either in granular or carbon block form). Any remaining
tastes and odors are removed from the product water
by post filtration.
- Automatic Shut Off Valve (SOV):
To conserve water, the RO system has an automatic shutoff
valve. When the storage tank is full (this may vary
based upon the incoming water pressure) this valve stops
any further water from entering the membrane, thereby
stopping water production. By shutting off the flow
this valve also stops water from flowing to the drain.
Once water is drawn from the RO drinking water faucet,
the pressure in the tank drops and the shut off valves
opens, allowing water to flow to the membrane and waste-water
(water containing contaminants) to flow down the drain.
- Check Valve: A check
valve is located in the outlet end of the RO membrane
housing. The check valve prevents the backward flow
or product water from the RO storage tank. A backward
flow could rupture the RO membrane.
- Flow Restrictor: Water
flow through the RO membrane is regulated by a flow
control. There are many different styles of flow controls.
This device maintains the flow rate required to obtain
the highest quality drinking water (based on the gallon
capacity of the membrane). It also helps maintain pressure
on the inlet side of the membrane. Without the flow
control very little drinking water would be produced
because all the incoming tap water would take the path
of least resistance and simply flow down the drain line.
The flow control is located in the RO drain line tubing.
- Storage Tank: The standard
RO storage tank holds up to 2.5 gallons of water. A
bladder inside the tank keeps water pressurized in the
tank when it is full.
- Faucet: The RO unit uses
its own faucet, which is usually installed on the kitchen
sink. In areas where required by plumbing codes an air-gap
faucet is generally used.
- Drain line: This line
runs from the outlet end of the reverse osmosis membrane
housing to the drain. This line is used to dispose of
the impurities and contaminants found in the incoming
water source (tap water). The flow control is also installed
in this line.
Diagram of a Reverse
Osmosis System with Basic Components:
Quality of RO Membranes and Filters –
They're not all alike!
While one RO System may look just like the
next in terms of design and components, the quality of those
components can be very different. These differences can
have a significant impact on the quality of the water the
system produces.
Here are some examples of questions you might
ask and consequences associated with "less than desirable"
quality.
- Has the manufacturer used sound methods?
What types of welds have been used in these plastic
products? Will they allow contaminated water to bypass
the filtration system? Will they allow the system to
leak?
- How has this filter or membrane been created?
Will it allow the water to 'channel' and, in effect,
bypass the removal component of this device?
- What about the quality of the 'fill'?
Are it's contents of a high enough quality to produce
the expected percentage of contaminant reduction? Carbon
quality, for instance, can have huge variances in reduction
capability, reduction capacity, and the sloughing of
'fines', which can prematurely clog or foul the RO Membrane.
- What are the manufacturer's controls on tolerances
or variations in specifications? If this component
is rated as a 1-micron filter will it truly filter out
everything larger than 1 micron or will it only do the
job 80% of the time? And, what if it actually filters
at a .5-micron rate? That will stop the system from
flowing -- clogging it and forcing filter replacement?
If this is a sediment filter and it fails the excess
sediment will clog or foul the RO Membrane.
- And in general - Are the materials
used in this product FDA or NSF (National Safety Foundation)
approved? If not, you might question their quality or
performance ability.
So, it becomes clear that the
quality of the components is the key to an optimal functioning
RO System.
Diagram of a Reverse Osmosis Membrane:
Where Can I purchase a Quality Reverse Osmosis
System or replacement filters and membranes?
We carry replacement filters and membranes
for most major brands of Reverse Osmosis systems. Click
Here to see the list of brands we carry.
We also have new Reverse Osmosis Systems
available to purchase. To see the features and benefits
of each type of system we offer Click
Here.
*Desalinate - The removal of dissolved
inorganic solids (salts) from a solution such as water to
produce a liquid which is free from dissolved salts.
**Osmosis – The
natural tendency for water molecules to pass through a semi
permeable membrane, from the side low in dissolved impurities
to the side high in dissolved impurities.
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