NOTE:
RO/DI = Reverse Osmosis/DeIonization Filter
DI filters are full of deionization resin. The resin basically bonds ions to them (calcium, sodium, etc, etc). There are Cation and Anion resins (ie; positive and negative ions).
Generally RO units have PREFILTERS on them, which includes carbon filters (Oh yeah GAC = Granulated Activated Carbon) basically the filters range from large to small. Filters are cheper than RO membranes, so they help lenghthen the life of the RO membrane by doing all the brute force filtering work.
Once the water is through the RO membrane, the DI filter will pick MOST of the remaining ions in the water. If the DI resins are seperate, you can actually recharge the resins with acids or bases. But if you have a MIXED BED RESIN DI filter, that means that both resin types are mixed together. The resin is in the form of little beads.
Did you mention DSB = Deep Sand Bed? (SOme people use sand beds at least 3 inches deep. The theory being that the deep sand creates anoxic (no oxygen) layers that convert Nitrates into Nitrogen or something).
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