Raising alkalinity
Sodium bicarbonate (baking soda) raises TA by about 10 ppm per 1.4 lb in 10,000 gallons and nudges pH up slightly. It is the same product as grocery-store baking soda, usually much cheaper in large bags than “alkalinity increaser”.
Lowering alkalinity
There is no chemical that removes alkalinity directly. The usual method is to add acid to bring pH down to about 7.0–7.2, then aerate to drive off CO2 and let pH rise again without TA coming back; repeat until TA is where you want it. Every 10 ppm of TA removed in 10,000 gallons takes about 26 fl oz of 31.45% muriatic acid in total.
What level?
Lower TA (50–80 ppm) means pH drifts up more slowly, especially in salt pools and pools with lots of aeration. Higher TA makes pH more stable against downward drift from trichlor. Typical ranges are on our target levels page.
Not professional advice. Results are estimates for residential pools and hot tubs. Read and follow product labels: add chemicals separately, to water (never water to chemicals), with the pump running, and retest before adding more. Commercial and public pools must follow local health codes.