Pool Alkalinity Calculator
How much baking soda raises your pool's total alkalinity, and how much to add first before you retest.
Why our numbers are more realistic
Baking soda math is well known, and most calculators get the dose about right. Where they differ is the target and the timing.
| Typical calculator | This calculator | Why it matters |
|---|---|---|
| Gives the full dose in one go | Starts with half, at most a 30 ppm rise, then retest | Arm & Hammer's pool guidance says to start with half to three-quarters, run the pump at least 6 hours, and retest. Raising alkalinity is easy; lowering it takes acid and repeated aeration. |
| One target range | Asks how the pool is chlorinated: liquid chlorine, mostly tabs, or a salt generator | Trouble Free Pool recommends 60–80 ppm for pools run on liquid chlorine or bleach. Chlorine tab labels say 80–120, because tabs use up alkalinity as they dissolve. Hayward, Pentair, and Jandy salt generator manuals also say 80–120 ppm. |
| Uses the test reading as is, whatever your generator's manual says | Asks whether your manual subtracts stabilizer (Pentair's does), and corrects the reading only then | Stabilizer shows up in the alkalinity test, and Pentair's manual measures its range without it. At 60 ppm CYA, a reading of 90 is then really about 70, so a 15,000 gallon pool needs 6.3 lb to reach 100, not 2.1 lb. The other manuals we read don't ask for this, so we don't do it unless yours does. |
How this works
Pounds of baking soda = (target ppm − current ppm) ÷ 10 × 1.40 × (gallons ÷ 10,000).
- 1.40 lb (about 22 oz) per 10 ppm per 10,000 gallons comes from the chemistry: alkalinity tests measure baking soda (sodium bicarbonate) as calcium carbonate. Arm & Hammer rounds it to 1.5 lb, about 7% more.
- Default target: the middle of the range: 70 ppm for liquid chlorine, 100 ppm for tabs or a salt pool (our choice). Enter your own under "Exact target".
- First addition: half the total, and never more than a 30 ppm rise at once. No label we found sets a cap, so 30 ppm is a planning limit: a test or volume error can't carry you far past the target, and lowering alkalinity takes acid and days of aeration.
- Corrected alkalinity (salt pools, when your manual asks): your reading minus a third of your stabilizer, as Pentair's manual says. Answer yes to the manual question and enter your stabilizer, and the target and dose are measured from the corrected number. Otherwise every choice, salt pools included, uses your reading as is: the Hayward and Jandy manuals we read, Trouble Free Pool's 60–80 and the tab labels' 80–120 don't ask for a correction.
- Tab pools: every tab adds stabilizer as well as chlorine, so the result reminds you to keep an eye on it. Tab labels' range is for the reading as is, but above about 80 ppm stabilizer, the third of it that shows up in the alkalinity test is large enough to matter.
Common questions
How do I lower alkalinity?
There's no quick fix. Add acid to bring pH down to 7.0–7.2, aerate (fountains, jets, spillovers) until pH rises to about 7.6, and repeat. In a salt water pool, don't use dry acid: Hayward says it can damage the cell. Follow the acid's label: wear goggles and gloves, pour it slowly into the deep end with the pump running, never mix it with chlorine or store them together, and keep swimmers out until a retest reads between 7.2 and 7.8.
Safety
- Add chemicals to water, never water to chemicals. Never mix pool chemicals with each other.
- Follow the product label. It overrides any calculator.
- Keep chemicals away from children, and don't add them just before people swim.
After you add it: order, waits and test limits
Order. Adjusting more than one thing? Do alkalinity first, then pH, then chlorine, with the pump running and at least 20 minutes between, retesting as you go. Keep calcium several hours apart from baking soda or soda ash, since together they can cloud the water. Never pour acid and chlorine in together.
| What you added | Retest after | Good to know |
|---|---|---|
| Liquid chlorine or bleach | About 30 minutes, pump on | Swim once a retest reads 4 ppm or below. |
| Cal-hypo shock | About 30 minutes for chlorine | Wait 24 hours before adjusting pH or alkalinity. Swim once a retest reads 4 ppm or below. |
| Acid (muriatic or dry) | 30 minutes to 2 hours, then the next day | pH creeps back up for a day as the water gives off carbon dioxide. Swim once a retest reads between 7.2 and 7.8. |
| Soda ash (pH up) | About 2 hours | Raises alkalinity too. |
| Baking soda | 6 to 24 hours | Run the pump at least 6 hours first. |
| Calcium chloride | 4 to 8 hours of pump time | Recheck chlorine too. |
| Salt | 24 hours, pump on | Brush the bottom so it dissolves. |
| Stabilizer (CYA) | 3 to 5 days | Don’t backwash for 48 to 72 hours. |
The short waits need the pump running; retesting the next day catches slow drift.
What your test can’t tell you.
- Most pH tests read only 6.8 to 8.2, so a reading at either end may be further out.
- Chlorine above about 10 ppm throws off the pH test and can bleach a chlorine drop test to a false low. Color-match DPD chlorine tests read only to about 5 ppm; an FAS-DPD drop test reads higher.
- Many kits can’t read stabilizer below about 20 ppm.
- Salt generator displays can be off by about 500 ppm; check with a salt test.
- Test strips read calcium only roughly; use a drop kit.
After heavy rain or an overflow, test free chlorine, pH, alkalinity and stabilizer before adding anything. Rain dilutes the water and can move pH either way, so test rather than guess. Strong sun and heat burn chlorine off faster, so in a hot, sunny climate test chlorine daily.
Filling from a well? Test the fill water at the spigot for metals first. Above about 0.2 ppm copper or 0.3 ppm iron, chlorine can turn the metals into stains. Add a metal sequestrant before you chlorinate, wait 3 to 4 days before shocking, and avoid copper-based algaecides.
From: Swim University on chemical order, Trouble Free Pool on adding chemicals, Trouble Free Pool on pH, Taylor Technologies FAQ, Swim University on metals and Trouble Free Pool on metals, plus the product labels and manuals in Sources.
What this doesn't cover
- Acid doses for lowering alkalinity.
- Full water balance (the saturation index).
- Commercial and public pools, which follow your state's health code.
Sources
- Arm & Hammer pool maintenance tips: 1.5 lb per 10,000 gallons raises alkalinity about 10 ppm; start with part of the dose and retest.
- Pentair IntelliChlor manual (Rev P, 2017): alkalinity 80–120 ppm; corrected alkalinity = TA − ⅓ CYA.
- Hayward AquaRite manual (Rev B): alkalinity 80–120 ppm.
- Trouble Free Pool recommended levels: alkalinity 60–80 ideal, 50–90 acceptable.
- HTH 3 in chlorine tabs, product label: alkalinity 80–120 ppm for pools run on tabs.
Numbers last reviewed: October 9, 2026.