OK. I checked both of the o rings you suggested. regreased the ones on the rotor disc.
I think the trouble is in the brine rinse cycle. This time I watched carefully -- the fill cycle ran for a long time and the water did not go up appreciably.
Now I had read in another thread in this forum that after draining the tank I was to add 3 gallons of water before I started it and I hadn't done that so I did (between these posts). So now we have a new variable. But anyway, I listened to and watched the first two cycles (fill and brining) and the now fuller tank DID go down and quite a bit... till it got to the 9ish inch line again where it stayed forever (even though it sounded like it was still draining and the drain line was emptying. It doesn't seem like the brine float ever even comes into play -- is that normal? Is that just an emergency shut off or something?
Anyway, it kept hissing like water was running through it and the drain in the sump pump kept draining, throughout the rest of the 2 hours (or whatever), but that water level in the brine tank never got below about 9 inches.
If that all sounds normal, I wonder if the "iron rinse solution" Sears offers is maybe the issue. We don't have HUGE iron, but we do have iron and I have never treated the resin bed with anything. Could it be that the resin just isn't keeping up?
Thanks for the non-condescending answer beirmech (beer mechanic auf deutsch?)