Since we are on the subject, I can add to what Will wrote.
The CTA membrane is the one that actually disintegrates in the presence of Chlorine. The C stands for cellulose, an organic material. We are not using that membrane.
The one we use is the TFC, Thin Film Composite. It's made of plastic from petroleum. It is more resistant to Chlorine. Using a carbon filter not only removes chlorine but other VOC's (Volitile Organic Compounds). FYI, gasoline contains VOC's. So the AC(activated carbon) filtering the water prior to the TFC membrane helps prolong it's life by removing specific harmful chemical substances.
Someone please correct me if I'm wrong, but I don't think it matters much to the membrane whether the sediment filter is a 1 micron or a 5 micron. Whether the particles are <1 micron or <5 microns, they all pass over the membrane and go out in the waste water. Particles lager than 5 microns would actually clog the larger screen which directs water over the microscopic screen membrane. The physical characteristics of the membrane and the Reverse Osmosis process actually gets more clogged with particles in two size categories. Those a lot larger than 5 microns and those a lot smaller than 1 micron.
For example, if you have ever screened dirt or gravel, its the particles that are just large enough to get stuck in the holes and not go through that cause the clogging. It works the same in a membrane, except that the membrane is trying to let molecules of water go through and stop larger molecules. Molecules are very tiny. Compared to 1 micron particles, molecules are like pea gravel among boulders.
I have taken apart many TFC membranes. They are all basically the same. The membrane unrolls into a ribbon of plastic sheet. Actually it's two ribbons rolled together. One ribbon has visibly larger holes that direct the clean tapwater into contact with the actual membrane and passing that water out the wastewater tube. High pressure forces water molecules through the ribbon of microscopic screen size membrane.
As a side note, the longer the ribbon, the higher the gpd(gallons per day) rating. A 24 gpd membrane is plenty of water. Most hobbyists don't need more water than that in a day. If more is needed, simply fill some large storage containers. You never know when you may need that water in an emergency if the city tapwater gets contaminated or stops flowing. RO water can be stored for a long time and is still safe to drink right out of the barrel.
Edited by Mark Peterson - October 20 2010 at 9:42am
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