If I decided at some point to add it, what would I be looking at, cost and difficulty-wise? Is it something you can do yourself, or does it require professional install?
Incidentally, the way I found out was because my controller kept beeping. When I asked the PB why it was doing it, he said something along the lines of 'It is set up for salt, but you don't have it. You can ignore the beep.'.