Most all the books that describe dripping Kalk tell us to use it to replace evaporated water from the tank. With that info, everyones drip rate will vary. If you find your sump full... too much. If you find it going down, too slow. I personally don't drip Kalk (but I may to help improve my current pH issue... I have high CO2 in my house and am bubbling outside air into the house [into the tank] to help bring CO2 down and pH back up).