I mix my salt in my water storage setup and just pump the water into that water change setup. It's purely a means of getting the water to the tank with no bucket carrying. I hate carrying buckets.
If i didnt have fire-breaks in my house frame, i would have an auto-water changer. Too much trouble and with this, it's really not a whole lot of work. I'll be testing it out tonight since I mixed a new batch of salt water yesterday so if there is a design flaw, I'll be sure to post it so you don't make the same mistake I did! xD