Use 1.5 pounds of baking soda per 10,000 gallons of pool water to raise total alkalinity by about 10 ppm. Baking soda, also called sodium bicarbonate, is the same active ingredient in most pool-store alkalinity increasers, and the ideal total alkalinity range is 80 to 120 ppm. The exact amount you need depends on two numbers, your pool volume and how far your current reading sits below target. The chart below pairs those two numbers so you can read your dose directly instead of doing the math.
How much baking soda to raise alkalinity by pool size
Find your pool volume in the left column, then move across to the gap between your current alkalinity and your target. The number in that cell is roughly how much baking soda to add. Each column assumes you are raising alkalinity by that many ppm.
|
Pool Volume |
Raise 10 ppm |
Raise 20 ppm |
Raise 30 ppm |
Raise 40 ppm |
|
5,000 gal |
0.75 lb |
1.5 lb |
2.25 lb |
3 lb |
|
10,000 gal |
1.5 lb |
3 lb |
4.5 lb |
6 lb |
|
15,000 gal |
2.25 lb |
4.5 lb |
6.75 lb |
9 lb |
|
20,000 gal |
3 lb |
6 lb |
9 lb |
12 lb |
|
25,000 gal |
3.75 lb |
7.5 lb |
11.25 lb |
15 lb |
|
30,000 gal |
4.5 lb |
9 lb |
13.5 lb |
18 lb |
If your reading is 60 ppm and you want 90 ppm, that is a 30 ppm gap. A 15,000-gallon pool at that gap needs about 6.75 pounds. Values between rows can be estimated by splitting the difference, since the dose scales evenly with both volume and ppm.
How to calculate how much baking soda you need
If your pool size is not on the chart, the math is straightforward. Take 1.5 pounds for every 10,000 gallons, then scale it by your ppm gap divided by 10. A 12,000-gallon pool that needs a 20 ppm rise works out to 1.5 times 1.2 times 2, or about 3.6 pounds. Round to the nearest quarter pound and add it in stages rather than all at once.
How much baking soda for a hot tub?
Hot tubs need far smaller amounts because their volume is low. A common starting point is about 1 tablespoon of baking soda per 100 gallons to raise alkalinity by roughly 10 ppm, though spa products and water vary, so treat this as an estimate rather than a fixed figure. Because a spa holds so little water, even a small overdose moves the reading fast. Start with less than you think you need, run the jets, and retest within an hour before adding more. Your spa manufacturer's guidance takes priority over any general rule.
How to add baking soda to raise pool alkalinity safely
Add baking soda by broadcasting it across the water surface with the pump running, never by pouring it into the skimmer. Spreading it in wide arcs helps it dissolve evenly instead of settling in one spot, and adding chemicals through the skimmer can be unsafe if you have a chlorinator or feeder inline.
Add no more than 1.5 pounds per 10,000 gallons in a single dose. This is the most useful guardrail for avoiding an overshoot. If the chart tells you to add 9 pounds to a 20,000-gallon pool, split that into three rounds rather than dumping it all in at once. If you are new to balancing water, start with three-quarters of your calculated amount, since adding more later is easy but pulling alkalinity back down means adding acid.
Keep the filter running for at least 6 hours so the baking soda blends through the full body of water. Wait 6 to 24 hours, then retest both total alkalinity and pH. If alkalinity is still below 80 ppm, repeat with another measured dose. Avoid adding other pool chemicals during this window so you can read the result cleanly.
How much baking soda you need depends on these 3 things
Three things change how much baking soda you actually need, and missing them is why some pools never seem to stabilize.
First, baking soda raises alkalinity and only nudges pH. If your main problem is low pH, the correct chemical is soda ash, also sold as pH increaser. Trying to raise pH with baking soda alone takes an impractical amount and sends alkalinity far past target.
Second, fixing low alkalinity often does not fully fix a low pH, and that is normal. Get total alkalinity into the 80 to 120 ppm range first, then adjust pH separately if it still reads low. A normal alkalinity result with a stubborn pH is expected, not a failure.
Third, if you use stabilized chlorine, your alkalinity reading can look fine while the part that buffers pH is too low. Cyanuric acid, the stabilizer in chlorine tablets and dichlor, also registers on a total alkalinity test, so a chunk of your reading is not actually buffering anything. The Pool & Hot Tub Alliance notes that total alkalinity should be corrected for cyanuric acid before adjusting pH. A common correction is to subtract about a third of your cyanuric acid level from the reading, so a pool testing 100 ppm with 90 ppm cyanuric acid has a corrected alkalinity near 70 ppm. If your pH keeps drifting despite a normal reading, you likely need more baking soda than the raw number suggests.
What happens if pool alkalinity is too low or too high
Total alkalinity protects pH stability, and pH stability protects both swimmers and equipment. When alkalinity is too low, pH bounces with every rainfall or busy swim day, and the water turns corrosive enough to pit liners and tile and eat at ladders and metal fittings. When it runs high, pH tends to climb, leaving water cloudy and prone to scale on tile lines. That is why the 80 to 120 ppm range is the target on both ends.
Balanced alkalinity also keeps chlorine working efficiently. The U.S. Centers for Disease Control and Prevention notes that a pH range of 7.0 to 7.8 gives chlorine the best conditions to kill germs while protecting pool surfaces, and many owners aim for a tighter 7.4 to 7.6 band.
Water balance is one half of pool maintenance. The other half is physical cleaning, since leaves, dirt, and organic debris raise the demand on your chlorine and can cloud water even when your chemistry reads fine. A cordless robotic pool cleaner like the iGarden Pool Cleaner K70 covers the floor, walls, and waterline on its own, so debris does not pile up while you focus on getting alkalinity and pH dialed in. It runs untethered, returns on its own when it finishes, and lifts out light after a quick self-drain, which makes it practical to run on a regular schedule rather than only after a problem appears.
FAQs
Can you put too much baking soda in a pool?
Yes. Overdosing pushes total alkalinity above 120 ppm, which tends to raise pH and can leave water cloudy with scale forming on tile and equipment. Bringing it back down means adding acid in stages, so dose conservatively and retest.
How long after adding baking soda can you swim?
Wait until the baking soda has fully circulated and dissolved, usually a few hours with the pump running. Retesting alkalinity and pH before swimming confirms the water has settled into range.
Does baking soda raise pH or just alkalinity in a pool?
It mainly raises total alkalinity and gives pH only a small, slow lift. For a real pH increase, use soda ash instead, which moves pH sharply while barely touching alkalinity.
Is pool alkalinity increaser the same as baking soda?
Functionally, yes. Most alkalinity increaser products list sodium bicarbonate as the only active ingredient, which is plain baking soda. The pool-branded version mainly adds a dosing chart on the label.