Is PH harder to maintain in RO water?

carbonates are used to help stabilize pH in RO. kh is the measure of carbonate hardness and are controlled by adding calcium carbonate(baking soda) or other carbonate. these caronates help to minimize pH swings.
driftwood, CO2 etc that cause a drop in ph do not change the TDS or carbonate hardness but rather introduce an acidic which changes the pH. This is of course all in a nutshell.
 
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