This is a topic I m VERY familiar with. I will tell you right now, if you do have water problems DO NOT buy the Rainsoft or even the Culligan water treatment systems. I have had both and they are both overpriced pieces of junk !! Rainsoft was at my house "fixing" the system every month and then charging me for warranteed parts !!
I finally had enough and look on the net and I found these guys
BUDGET water softener - water treatment system - iron filters - water softner Their system was half the price and actually works !!! I have not had a problem since. My system uses pyrolox for the iron content and I never have to buy salt or any other additive.
I highly recommend them especially for their pricing.