Total alkalinity (TA) is the measure of your pool waters ability to resist pH changes. Technically, TA is defined as the sum of all of the concentrations chemical ion species in your pool water that can react with (or consume) a hydrogen ion (H+).
The vast majority of your water’s alkalinity comes from the dissolved inorganic carbon (DIC) in it. DIC is primarily in the form of carbonates – dissolved or aqueous CO2, bicarbonate ion (HCO3-) and carbonate ion (CO32-). However, cyanurates from your stabilizer (cyanuric acid) as well as borates contribute to your water’s alkalinity. For both carbonate and cyanurate alkalinities the buffering intensity increases with a decrease in pH while borate is the opposite where buffer intensity increases with an increase in pH.