Use the calculator from the Chemistry forum, don't add it all at once. If your calcium is low just by adding kalk is not going to raise it much. You should drip at nights only when they ph gets low a PH monitor is very helpful. PH on kalk is about 12 or higher. I bet your alk is low too. You need to check alk, calcium and magnesium because these are tight together. To make a major correction use calcium chloride (dowflake) or turbo calcium and get the alk right, then use kalk to maintain. Check every week and see how much your system uses. Some times using kalk is not enough to keep up with the demand of the system. If you can find Pickling lime a the grocery store get that it's a lot cheaper than buying kalk and it's the same thing.