Pool alkalinity calculator
Raise total alkalinity with baking soda or bring it down with acid and aeration. Enter your test and target, and see the dose and how pH will react.
Lower alkalinity: acid + air
- Add the per-round acid to bring pH to about 7.1. That also removes some alkalinity.
- Aerate: point returns up, run waterfalls or a fountain. pH climbs back without adding alkalinity.
- When pH is back to 7.6–7.8, repeat. Test TA every couple of rounds.
Chemical safety: read the product label first and follow it where it differs from this page. Add acid to water, never water to acid. Never mix chlorine products with acid or with each other, not even in a bucket. Add one chemical at a time with the pump running, wait at least 30 minutes (acid and chlorine: until the next test), and retest before topping up.
Alkalinity is a buffer: see it soak up acid
Pour the same amount of muriatic acid into three 10,000-gallon pools that all start at pH 7.8. The only difference is total alkalinity. Drag the acid dose and compare where each lands.
Low alkalinity leaves the water with nothing to absorb the acid, so pH crashes. That’s the “pH bounce” owners fight in low-TA pools. High alkalinity barely budges, so pH rises again quickly as CO₂ escapes. The middle is easiest to live with.
TA 40 ppmpH 7.08
TA 80 ppmpH 7.33
TA 140 ppmpH 7.48
Bars show pH on a 5.0–7.8 scale. Model: carbonate equilibrium at 25 °C, no stabilizer.
Questions pool owners ask
How much baking soda raises alkalinity in a pool?
About 1.4 lb (22 oz) of baking soda raises total alkalinity by 10 ppm in 10,000 gallons. For a 20,000 gallon pool, that’s 2.8 lb per 10 ppm. Add no more than about 10 lb per 10,000 gallons at a time, then retest after a few hours.
What should total alkalinity be in a pool?
Most pools do well between 60 and 120 ppm. Liquid-chlorine and salt pools often run best at 60–80 ppm because pH rises more slowly; trichlor-tab pools usually need 80–120 ppm to offset the acidity of the tabs. Plaster pools should be checked with the LSI.
How do I lower total alkalinity?
Add acid to bring pH down to about 7.0–7.2, then aerate (waterfalls, jets pointed up, fountains) to push pH back up without adding anything. Each cycle removes some alkalinity. Repeat until TA is where you want it. It usually takes several days.
Does baking soda raise pH too?
A little. Baking soda has a pH of about 8.3, so it pulls pool pH gently towards that. The calculator shows the expected pH after your dose.
Does stabilizer affect alkalinity?
Yes. Test kits measure cyanurate as part of total alkalinity. At normal pool pH, roughly a third of your CYA reading shows up as alkalinity, so a pool with 90 ppm TA and 60 ppm CYA has only about 70 ppm of carbonate alkalinity.