Puckdropper wrote:
I've done some Google searching, checked the archives of this group
for relavent recent discussion, and have thus far come up with
nothing useful.

We have a water softener and dehumidifier that drain in to the sump
pump. The sump pump output pipe froze, causing the discharge from the
softener regeneration to back up into the basement. I'm looking for
a high water alarm that can cut the power to these devices in case
something happens again.

Does anyone know of such a thing?

Since it has plenty of pressure behind it, why not plumb the softener directly
out with its own downsloaping drain? Make sure that any pipe exposed to freezing
temps is as short as possible and flows only downward to the outlet, and is well
insulated.