[Samw]

Originally Posted by GMGQ

Interesting. I thought RO/DI's were meant to take out the solids in the tap water, not organics?

I guess it depends on the membrane that you bought: CTA, TFC, or High Removal.

http://www.drsfostersmith.com/produc...fm?pcatid=4467

Materials Removed CTA Percent(%) TFC Percent (%)
Hardness          93 - 95        93 - 97
Heavy Metals      94 - 96        95 - 98
Ammonium          85 - 90        80 - 90
Phosphate         85 - 97        95 - 98
Nitrate           50 - 70        90 - 95
Silicate          80 - 90        92 - 95
Bacteria          NA             >99

http://www.peteducation.com/article....articleid=2890

CTA - Cellulose Tri-Acetate membranes are organic and have a slightly lower TDS removal rate of 88-94%. Because they are organic, use them only with chlorinated water (water from a municipal source) in order to keep them clean and free of damaging molds and bacteria. They do not filter out chlorine, so allow the chlorine to dissipate out of filtered water, or treat it with a chemical dechlorinator.

TFC - Thin Film Composite membranes are synthetic and remove between 94-98% of TDS. These units contain a carbon pre-filter to protect the membrane from chlorine damage. Use these membranes for water with or without chlorine.

High Removal Membranes are synthetic membranes with much higher removal rates, between 97.5-99%, and are especially adept at removing silicates. These units also contain a carbon pre-filter to protect the membrane from chlorine damage. Use these membranes for water with or without chlorine.

http://www.algone.com/reverse_osmosis.php

The two types of membranes:

Cellulose Triacetate (CTA)
This film is acceptable for treating tap water that contains chlorine/ chloramine. In fact CTA needs an antibacterial substance in the water, as the film is not good in removing bacteria. CTA should not be used if the water is hard (500 ppm) or has a pH above 8.5

Thin Film Composite (TFC)
This film is acceptable for hard water and can filter out bacteria. It is also well suited in holding back nitrates, phosphates, and silicates. Chlorine/ chloramine on the other hand can not be tolerated. Using a TFC membrane with tap water (public water) you must pre-filter the water to eliminate chlorine/chloramine (i.e. carbon filter).