It goes through a water softener to remove minerals before being used as make up water for the boilers. From what I've heard if you taste it, it tastes sweet and that's where the name comes from.
I think that's a crock, but I'm not willing to try anything full or salt and zeolite. The zeolite pellets are like ice if they get on the floor. Tiny little beads and you will fall and bust your ass.