If you have read my previous discussion, I have two pools that in order to maintain Alkalinity over 70 I am adding 50lbs of Sodium Bicarbonate ever few weeks. The other pools in my complex have CO2 to help regulate pH in addition to muriatic acid. My pools use only muriatic acid. The pools with CO2 do not require Sodium Bicarbonate and it has been explained to me that the CO2 that it helps maintain and raise Alkalinity. However from my research CO2 becomes carbonic acid in water affecting pH but has no affect on Alkalinity. Can anyone help clear up the question of CO2's affect of Alkalinity?