Pool Total Alkalinity Guide — How to Adjust TA
Why the 80–120 ppm buffer decides whether your pH stays put or bounces.
Total alkalinity (TA) is the shock absorber under your pH. It measures the water's reserve of bicarbonate and carbonate, reported in ppm as calcium carbonate. With too little reserve, pH lurches with every rainstorm and chlorine dose; with too much, pH wedges itself high and shrugs off correction. The alkalinity calculator works the 80–120 ppm band from either direction.
Raising TA: The Baking Soda Figure
The calculator uses 2.24 oz of sodium bicarbonate per ppm per 10,000 gallons. Worked example with the tool's own defaults: a pool reading 60 ppm with a 100 ppm target needs a 40 ppm rise — in a 20,000-gallon pool that is 40 × 2 × 2.24 = 179 oz, just over 11 pounds of baking soda. Splitting a dose that size into two or three additions with circulation in between lets you confirm the trajectory before committing the full amount.
Lowering TA: Acid and Patience
Coming down uses muriatic acid at 2.56 fl oz per ppm per 10,000 gallons. A 20,000-gallon pool at 160 ppm aiming for 100 ppm computes to 60 × 2 × 2.56 ≈ 307 fl oz — about 2.4 gallons of acid. That number is a total budget, not a single pour: acid depresses pH at the same time it consumes alkalinity, so large corrections are spread over multiple days of dosing, circulating, and retesting both values.
TA and pH Are a Coupled System
Every acid dose moves both numbers; every aeration session nudges pH back up without touching TA much. This is why the calculators keep the jobs separate: the alkalinity tool prices a TA change in acid or baking soda, while the pH tool prices a pH change (6.5 fl oz of muriatic acid per 0.1 pH per 10,000 gallons, calibrated at TA near 100 ppm). Correct TA first, let the water settle, then trim pH — doing it in the other order usually means doing it twice.
The CYA Correction Hiding in Your LSI
Not all measured alkalinity buffers the same way. Stabilized pools carry cyanurate alkalinity, so the LSI calculator works with corrected alkalinity = TA − CYA ÷ 3. A pool testing 90 ppm TA with 90 ppm of stabilizer behaves like a 60 ppm pool in the water-balance math. If your LSI keeps coming back lower than your TA reading suggests, this correction is usually the reason.
FAQ
Is plain baking soda really the same as alkalinity increaser?
Chemically yes — sodium bicarbonate is the active ingredient in both, and the calculator's 2.24 oz per ppm per 10,000 gallon figure applies to either. Check the label for 100% sodium bicarbonate and you can dose from the grocery aisle.
Why did my pH crash when I lowered alkalinity?
Because the same acid drives both down. The fix is sequencing, not a different chemical: dose part of the acid budget, circulate, retest TA and pH together, and let aeration recover pH between rounds rather than chasing it with soda ash.
What target should I actually type in?
100 ppm is the tool's default and the center of the 80–120 ppm band. Saltwater pools often run leaner, around 60–80 ppm, because a salt cell continuously pushes pH upward and a lighter buffer keeps that rise manageable.