OK here goes nothing.
The system works like a regular ATO. There are two float switches in the sump which use a 12v controller and relay. The two switches are set side by side and are wired in series. They are set this way for redundancy so that both must make contact for any water to flow and if either fails then no water flows.
I use two 20g containers for holding my saltwater and my kalkwater.
The 12v converter is on a digital timer that turns off at 6pm (back on at 630). At 605 an aqualifter in the sump turns on and runs for about 30 min draining 1.5g of water into a small holding tank.
About 630 this one timer and pump shut off and the saltwater holding tank timer and pump come on. It refills the sump until the float switches turn it off. About 7pm this timer shuts off the pump and the regular ATO form the kalk systems back on. It may sound a little complicated, but it all works off one 12v relay and the digital timers.
I have been empting the small container of waste water each night by hand but plan to add another timer to empty it into the washer drain when I have time.