Pool Total Alkalinity Calculator (TA Adjustment)

Total alkalinity is the pH buffer. TA does not change how the pool feels. What it controls is how stable your pH is. Low TA means pH bounces around with every chlorine addition. High TA locks pH at the high end and resists adjustment.

Target range: 80-120 ppm. Some pool stores push 100-150. The 80-120 range is closer to optimal because it gives enough buffering without making pH adjustments hopeless. Saltwater pools are the exception: a salt cell drives CO₂ off and pushes pH upward all season, so most owners run below the usual band, at 60-80, which makes the constant pH corrections much smaller.

To raise TA:

• Sodium bicarbonate (baking soda) is the standard. Cheap, safe, and gentle.
• Reference dose: 1.4 lb per 10,000 gallons raises TA by 10 ppm. Also raises pH very slightly.

Both dose figures on this page come out of the same stoichiometry rather than a chart. Ten ppm of alkalinity in 10,000 gallons is 379 grams as calcium carbonate, which is 7.56 equivalents. Baking soda supplies one equivalent per 84 grams, so you need 635 g, or 1.4 lb. Muriatic acid consumes one equivalent per mole, and 31.45% acid is 10 mol per litre, so 7.56 equivalents is 756 mL, or 26 fluid ounces.

To lower TA:

• Muriatic acid is the only practical option for backyard pools. Pool acid lowers TA and pH together, but with aeration the pH climbs back while TA stays down.

Reference dose: 26 fl oz of 31.45% muriatic per 10,000 gal lowers TA by 10 ppm.

The aerate-afterwards method, and the myth attached to it:

1. Add the acid slowly, with the pump running, poured in front of a return jet so it disperses immediately.
2. Let it circulate for half an hour. Both pH and TA will have dropped.
3. Aerate hard: waterfall, fountain, spa jets, or return eyeballs turned up to break the surface.
4. Aeration drives off dissolved CO₂, which raises pH back up while TA stays where the acid put it. Repeat over several days until TA is where you want it and pH has come back to 7.5.

You will read elsewhere that you should pour the acid into one concentrated spot with the pump off, to do “localised damage” to the alkalinity. This does nothing. Acid neutralises bicarbonate stoichiometrically wherever it ends up, and the same quantity lowers TA by the same amount whether it goes in as a column or spread across the pool. The step that actually separates TA from pH is the aeration afterwards, not how you poured it.

Meanwhile the advice is genuinely harmful. Concentrated hydrochloric acid sitting in still water etches plaster, bleaches vinyl liners, and corrodes anything metal it settles against. Pump on, poured slowly, always.

Worked example. 20,000 gal pool, current TA 60, target 90.

• Raise needed = 30 ppm
• Sodium bicarb dose = 1.4 lb × (30/10) × (20,000/10,000) = 8.4 lb

That is a big dose. Spread it over 2-3 days to avoid a pH spike.

Common mistake. People chase TA and pH at the same time and end up cycling. Fix TA first (get into the 80-120 band), then adjust pH separately. Treat them in order, not together.

Saltwater note. Salt cells generate hydroxide ion which slowly raises pH and can pull CO₂ out. Saltwater pools tend to drift toward high pH, so most owners run lower TA (60-80) to make pH easier to manage.