I should write a FAQ..
Your unit has in order..
1) sediment filter. Gets the rocks and dead algae and bug bodies and rust flakes out of your city water. Floaters.
2) loose carbon filter. To start removing organic materials like chlorine, and fluoride, and other stinky stuff dissolved in the water.
3) carbon block filter. This fore-shore-Rocky removes any other traces of chlorine and fluoride, etc., as any of the two former chemicals will gut your membrane promptly.
4) The RO membrane. The prefiltered water is passed by the membrane and some passes thru. It is called 'The product'. 4/5's of the water running thru the membrane flushes the now concentrated minerals that were blocked from leaving in the Product water out as waste. It is called "The Brine". This stuff generally goes down the drain, or to your plants, or you can drink it, as it is much cleaner than your tap water. Taste it sometime after your unit has run. Taste your tap water then taste this. You will see an improvement.
The Product is the extremely clean RO water. This is what you would drink and make coffee,(yuck!), with. Mine is plumbed under my kitchen sink and we drink and cook with about 3 gallons a day.
The RO process blanket removes 93 to 98%,(depending on your wallet), of the dissolved substances that came to it from #3 (above).
It should be noted that the membrane wears out eventually. The membrane is destroyed if allowed to dry out or if it gets moldy.
5) The DI column. The product is run next thru the Ion Exchange Column, normally just called, 'The Column' . This is to remove, thru a process called chelation, any minuscule amount of remaining Ions that made it thru the RO process,(remember those 7-2%?).
The column removes these remnants. The resulting water is pretty much just water. Angry water... Water that is so stripped of everything that it will grab anything it can. In fact really pure water is considered corrosive due to this, but that's another subject.
It should be noted that the column becomes exhausted once it has captured all the ions it can. Of course the better your RO system the longer the column lasts.
It should also be noted that the horizontal, itty bitty, column, you purchased, will likely be exhausted relatively soon. Horizontal columns also tend to let a lot of water pass thru OVER the settled media and hence NOT actually put out great DI water. Vertical columns don't generally suffer from this.
6) Carbon Polishing Filter. This last item is supposedly for taste. In reality having a really clean RO/DI output you shouldn't need a follow-on Polishing filter. If it is really after the DI cartridge it is there only for preventing any of the media from a buggered column from carrying on to the end use.
Normally as mentioned earlier you should NOT be drinking DI water only RO water. If you set up your system for drinking you must set it up so that the product goes into a bladder tank. This is to allow you to, say, pour a glass of water. Not wait forever while the small dribble of product is being produced. Well the bladder tank is rubber lined and the rubber wants to get into the pure RO water pretty bad. You could taste this if enough gets in. So! You want to put a polishing filter between the bladder/storage tank and your drinking water tap. That is it's typical function.
Now back to your original question. The carbon filters typically put out a few gallons of black filthy looking water the first time you run water thru them. This is very tiny carbon power grains from the manufacturing process. You DO NOT want this stuff going into your membrane. The membrane has zillions of tiny holes in it. These would be bad to fill with carbon power. Normally you should undo the hose coming from #3 and turn on the water supply. Run water until you can see NO carbon fines coming out of the hose from #3. Turn off your supply and then hook up this hose. Disconnect the hose going from #4 to #5 Turn the supply on and run at least 2 gallons out of this hose. If you have a TDS meter check this product water after a few gallons. It should read below 10ppm in fact hopefully with a great system it will read 0ppm. If this is the case then turn off the supply and hook this hose up. Turn the supply back on and run another gallon out of the DI /end of the system. Check the TDS here. It better dang well be 0ppm ALWAYS. OK you can now use the RO/DI water for your aquarium. Remember don't drink it.
