Pool Alkalinity Calculator
Baking soda to add
6.3 lb
Add 6.3 lb of baking soda (sodium bicarbonate) to raise total alkalinity in 15,000 gallons from 60 to 90 ppm.
- TA increase
- 30 ppm
- Rate
- 1.4 lb per 10,000 gal per 10 ppm
- Never mix pool chemicals with each other, wet or dry.
- Always add chemicals to water, never water to chemicals.
- Follow the manufacturer's label. It overrides any calculator, including this one.
How it's calculated
Total alkalinity is reported in ppm "as calcium carbonate". One milliequivalent per liter equals 50.04 ppm, so the calculator converts your change into milliequivalents and then into product:
Muriatic acid at 31.45% supplies 0.3 mol of acid per fluid ounce. The baking soda figure works out to about1.4 lb per 10,000 gallons per 10 ppm, a handy number to remember.
Worked example
A 15,000 gallon pool tests at 60 ppm TA and you want 90 ppm:
- Increase: 30 ppm ÷ 50.04 = 0.5995 meq/L.
- × 56,781 L = 34,040 meq.
- × 84.0 mg = 2,859,625 mg = 6.3 lb of baking soda (2.9 kg).
Going the other way, lowering the same pool from 140 to 100 ppm takes about 1.2 gal of 31.45% muriatic acid, added in stages over a few days with aeration in between.
Why alkalinity matters
TA is the pool's pH buffer. Too low and pH swings with every rainstorm or chlorine dose; too high and pH keeps creeping up, which wastes acid and encourages scale. Baking soda is the gentle way up; acid plus aeration is the controlled way down.
Common alkalinity problems
- pH crashes after rain or a big chlorine dose: TA is probably below 60 ppm. Raise it with baking soda in steps of about 20 ppm.
- pH climbs every few days: TA is likely high for your pool. Salt pools and new plaster usually settle best at 60–80 ppm.
- TA reading jumps around: check the test. Titration kits are far more precise than strips, and CYA adds to the TA reading (roughly a third of the CYA level).
Change per 10 ppm of total alkalinity
| Pool size | Baking soda (+10 ppm) | Muriatic 31.45% (−10 ppm) |
|---|---|---|
| 10,000 gal | 1.4 lb | 25.6 fl oz |
| 15,000 gal | 2.1 lb | 1.2 qt |
| 20,000 gal | 2.8 lb | 1.6 qt |
| 25,000 gal | 3.5 lb | 2 qt |
| 30,000 gal | 4.2 lb | 2.4 qt |
Frequently asked questions
How much baking soda do I add to raise alkalinity?
About 1.4 lb of baking soda raises total alkalinity by 10 ppm in 10,000 gallons. For 20,000 gallons and a 30 ppm increase, that is about 8.4 lb.
What should total alkalinity be in a pool?
Most pools do well between 60 and 120 ppm. Aim for 80–100 ppm (60–80 for salt pools). Pools with salt generators or fresh plaster often run better at the low end because high TA makes pH climb.
How do I lower total alkalinity?
Add acid to lower both pH and alkalinity, then aerate (fountains, jets pointed up, waterfalls) to bring pH back up without raising alkalinity again. Repeat until TA reaches the target. Never let pH drop below about 7.0 during the process.
Does baking soda raise pH?
Only slightly. Baking soda has a pH around 8.3, so it nudges pool pH toward that but mostly adds alkalinity. To raise pH noticeably, use soda ash.
Should I adjust pH or alkalinity first?
Alkalinity first. TA is the buffer that holds pH steady, so fix it first, wait a few hours, then fine-tune pH with the pool pH calculator.
Related calculators
- Pool pH CalculatorAcid or soda ash to hit your target pH.
- Pool LSI Calculator (Saturation Index)Is your water corrosive, balanced or scaling?
- Pool Calcium Hardness CalculatorCalcium chloride to raise CH, or drain to lower it.
- Pool Volume CalculatorGallons or liters for any shape, including sloped floors.
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