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.