How do I add kalkwasser with my top off?

[fishnugget]

I have a top off ro/di that goes right into my sump with a float. I have an MRC2 calcium reactor. My friend has the same and doses 2 times a day with 1 gallon of kalkwasser mixed in a 1 gallon jug.
He says this is great for his corals. I don't understand why this is needed and what it does if he has a calcium reactor which maintains calc and alk. What is the advantage?

How can I do this also without having to mix jugs daily. I added a calc reactor to avoid manual ESV dosing. I always forgot to do it.

My chem is:

210 gallon tank
PH 8.1-8.3
dkh 12.8
Calcium 430

[Randy Holmes-Farley]

The advantage of using limewater along with a CaCO3/CO2 reactor is that the limewater will boost the pH back up. If you can maintain pH 8.1 to 8.3, then there is no need. Many folks find the pH drops in the the 7's without limewater.

I dose limewater from a 44 gallon trash can and a slow pump (3 gallons per day) to replace all evaporate water. It is best dosed very slowly, such as dropwise.