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Let me offer a little RO primer first so you can compare the offerings of different RO system manufacturers.
The key to a RO unit is the membrane itself. If it is a TFC (thin film composite) poly amide type membrane (typically mfg'd by Filmtec* sub of the Dow Chemical Company) then you must have a carbon prefilter to remove chlorine. If it's a CA membrane (cellulose Acetate) then a carbon prefilter is not necessary. However, it's still a good idea to have a carbon filter to remove the residual chlorine before use in an aquarium. A 5u filter to remove particulate is also critical as it removes 5 micron or larger particles from clogging the membrane. A TFC membrane is more tolerant of bacterial decomposition than a CA membrane. The rejection rate (amount of "stuff" removed from the feed water) of a TFC is also better than a CA membrane. The recovery rate is also important (the amount of product water produced versus the feed water). Typical recovery rates are around 25-33% meaning you waste 3 gallons of water for every 1 gallon of RO water produced. Some suppliers may not even know the answers to some of these issues.
I'd recommend:
A bare bones TFC system, with a Carbon filter and a 5 micron prefilter is sufficient for the quality of water you'll need. I prefer having a Mixed Bed DI unit at the end to polish the water as well. However a DI (ion exchange) unit requires more maintenance and a greater understanding to operate. The newer color changing DI units makes that understanding easier.
I'd ask the Ebayer whose membrane they are using first and go from there. Pressure guages and purity monitors are neat extras and a way to determine if a membrane needs replacement.
Justin, If you have further questions feel free to call or PM me. - Dale
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Dale
Last edited by phishschtick; 12-25-2003 at 11:10 PM.
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