[ccjohnson]

The way Tommy Key at Newell explained it to me, was that you don't ever add anything to it.  Just back flush  every couple of months or so. Seems to work pretty good so far.  Only issue is that the timed valve leaks some.  But I just cap the back-flush discharge port when not back-flushing.  Usually just do a 20-30 min back flush when I see some spots start to develop on shower door.   Hand written directions on wet bay say 10 mins.  One of these days when I feel ambitious I will check total hardness before and after back-flushing just to see if it is actually working.  For now, just thinking it works is ok.  I know Tommy said that they are not available anywhere anymore.  If yours is functional Hoosier, I might be interested in getting it for a spare if you don't want to keep it.