Kalk Dripping

Where is the best place to drip the kalk into your system? I am pretty sure
i read you dont want to drip it into
your tank. I was dripping it into my sump right where my return pump was.
However recently I started driping into the back of my overflow just out of
convience. Should I be dripping before or after the skimmer? I was before
and now and after. Just thought I would ask for some opinions on this.