salt for softner

If the instructions say table salt then that is what I would suggest that you use. Table salt will dissolve much more quickly than rock salt or salt pellets. In order for it to do it's job the salt must be completely dissolved in water before it starts to remove the contaminates from the resin beads. I use non iodized table salt in my softener and letting it sit for maybe 10 minutes and vigorously shaking the cylinder a couple of times before slowly back flushing the unit. Takes all of 20 minutes.

As plain ol' table salt is the cheapest, I don't know why you'd want to use anything else. Besides, all it's doing is stripping the hard water deposits off the the gold and flushing it all away. There isn't any residual effect that I know of. Although... there have been folks that claim there are other substances that can be used if, for example, high blood pressure is a concern, Potassium Chloride can be used... but it is more expensive.