Jreed,
I cannot answer to your question regarding the resin media in the post just above. However, I would like to spur you on to consider a B.I.R.M. iron removal filtration system. I read some of your other posts in the thread links up above and thought I would at least try to inform you of another iron (an manganese) removal process that may help you reduce operation costs. If I read everything correctly, you are using an iron removal system that requires rejuvenation with a brine of some sort. If this is correct, I would like to tell you about B.I.R.M.
BIRM is a natural mineral that is coated with a catalyst. This mineral, with its catalyst coating, reacts with the ferrous iron (the type of iron that is dissolved in many wells) and the dissolved oxygen in the water to form ferric iron.
The ferrous iron cannot be removed from the water by mechanical filtration. It has to be converted to ferric iron first in order for it to be removed by a filter mechanism. The BIRM media (and its catalyst coating) and the dissolved oxygen perform this conversion process.
That beneficial process is not the end of the BIRM media's duty, however. Once the ferrous iron has been oxidized to ferric iron, the BIRM media actually serves as the mechanical filter to trap that iron within the media.
To remove the buildup of the ferric iron, you simply backwash the BIRM with water straight from the well. No sodium chloride, no sodium hydroxide, no potassium permanganate, no chemicals required what-so-ever. Only vigorous backwashing with fresh water is all that is required.
To top this advantage, the BIRM and its catalyst coating is never depleted unless it is fouled by chlorine or some other agent. It will virtually last forever (within reason).
If this idea interests you, check out B.I.R.M. with Google. I use it! My friends who have iron water troubles use it! I swear to you, it works really great! It is not too expensive and you can build your own DIY filter mechanism for it or you can convert a discarded water softener to put it in. If the mechanics and electronics of the softener still operate, you are home free! Just dump out the used water softener resin beads and refill it with BIRM!
Gordy