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Reverse Osmosis Filter

Two Basic Types:
Reverse Osmosis systems usually have one of two types of membrane, CTA or TFM. Each of these membranes has a particlar characteristic and performance.

CTA : Cellulose Tri Acetate
Generally, CTA membranes are used on chlorinated water supplies with a Total Dissolved solid content below 800 ppm.

TFM/C : Thin Film membrane/composite
Reverse Osmosis systems fitted with Thin Film composite (TFM) membranes are idealy used on non chlorinated water supplies with a higher TDS content. They are also used on chlorinated supplies where a faster water production is required or a higher water purity is needed. When used on chlorinated water supplies an Activated Carbon prefilter is included to remove the chlorine prior to it entering the membrane. TFC membranes have superior strength and durability as well as higher rejection rates than CA/CTA membranes. They also are more resistant to microbial attack, high pH and high TDS. CA/CTA's have a better ability to tolerate chlorine

Water pressure in most residential areas should be at least 400 kpa or 60 psi
The AS/NZS 3500 Standards state in part that:
The minimum working head at the furthermost .... outlet shall not be less than 50kpa (5 m head)
It also goes on to say :
The maximum static head shall not exceed 500kpa (50 m head)

Four stages of filtration:

1. Sediment removal. Takes out the finer particles that shorten the life of the other filters
2. Removes chlorine that would otherwise damage the reverse osmosis membrane and other chemicals (activated carbon).
3. Reverse osmosis membrane removes chemicals that other filters let slip through (see reverse osmosis)
4. Polishing filter. This takes out the things that reverse osmosis, by its nature, must let through.

Replacement membranes are approximately $100.00 (please confirm this with us as prices DO vary)

GPD = Gallons per day. To convert to Litres, multiply X 3.8.
i.e. 50 GPD equals 190 litres per day (based on a pressure of 100 psi or 700 kpa) These units are rated in GPD because they are manufactured for the very fastidious U.S. market

How RO Works: In Practice
Long sheets of semipermeable membrane are ingeniously sandwiched together and rolled up around a hollow central tube in a spiral fashion. This rolled-up configuration is commonly referred to as a spiral wound membrane or module. They are available in a large selection of sizes for processing different quantities of water. Typically, a module for home water treatment is as small as 2" diameter and 10" long, while one for industrial use may be 8" diameter and 48" long.

Now that the membrane is in a usable form it must be put in some type of container (called a pressure vessel) so pressure can be maintained on its surface. It is this pressure that supplies the energy to force the water through the membrane, separating it from the impurities. The most amazing aspect of RO is that the contaminants left behind are automatically diverted to a waste drain so they don't build up in the system as with conventional filters and purification devices. This is accomplished by using a part of the unprocessed water (feed water) to carry away the rejected impurities to the drain, thus keeping the membrane clean. The flow of impurities to the drain is often referred to as reject water. This is the secret to why RO membranes can last so long and perform like new with minimum maintenance even after years of operation. It is also the reason behind the low cost of producing RO water.

The ability of the RO membrane to filter out contaminants is generally expressed as a rejection rate (percentage of contaminant rejected). The rejection rate of an RO filter can depend on a number of factors, such as water pressure, temperature, the pollutant concentration and chemical properties of the pollutant. Membrane type and operating conditions will also affect the degree of pollutant removal. That said, RO is effective in eliminating or substantially reducing a wide variety of contaminants. It will allow the removal of particles as small as individual ions. The pores in a reverse osmosis membrane are only approximately 0.0005 micron in size (bacteria are 0.2 to 1 micron & viruses are 0.02 to 0.4 microns). Reverse Osmosis has the greatest range of contaminant removal among filtration techniques commonly used to treat household water and perhaps the only one that will remove things as small as bacteria and viruses (except distillation).

V = L x W x D x 0.00433

where V is the symbol for the Volume in gallons, L for the Length, W for the Width, D for the Depth, and the 0.00433 is a so-called conversion factor that converts the answer from cubic inches to gallons.

Removes the following contaminants:

Click here to view the specifications for commercial & industrial reverse osmosis systems.