From my understanding the alkalinity in kalk is dosed by hydroxide. When the hydroxide reacts with dissolved co2 it creates carbonate and bicarbonate. When the hydroxide no longer has co2 to react with it will precipitate. You may be adding too fast for the co2 in the chamber you are dosing into to replenish. I drip fully saturated kalk at all times and while it completely replenishes my CA I still have to supplement the alk.