Guide
How to raise or lower pool alkalinity
Updated October 21, 2026
Written by Richard Ellis, Certified Pool Operator
Short answer
Keep total alkalinity around 80 to 120 ppm. To raise it, add sodium bicarbonate (baking soda) a little at a time with the pump running. To lower it, add muriatic acid to bring the pH down, then aerate the water so the pH rises again on its own, and repeat; alkalinity falls a little each round.
Alkalinity is the reading most people skip, and it is the one that decides whether the pH stays where you put it. Too low and the pH swings all over the place. Too high and the pH keeps creeping up no matter how much acid goes in. Here is how to move it in either direction.
What does total alkalinity do in a pool?
It buffers the pH. Alkalinity is the water's resistance to pH change, so it is what keeps the pH from jumping every time it rains or a chemical goes in. Get it right first and the pH gets much easier to hold.
What should total alkalinity be?
About 80 to 120 ppm for most pools. That is the range in our chemical levels guide, and the one Hayward's AquaRite manual gives for salt pools too.
How do you raise alkalinity in a pool?
Add sodium bicarbonate, sold as alkalinity increaser. Dose it for your gallons by the label, spread it across the surface with the pump running, wait several hours, and test before adding more. It raises alkalinity a lot and the pH only a little.
Can you use baking soda to raise pool alkalinity?
Yes. Alkalinity increaser is sodium bicarbonate, which is exactly what household baking soda is. The only real difference is the size of the bag.
How do you lower alkalinity in a pool?
With acid and air. Add muriatic acid to bring the pH down to around 7.0 to 7.2, which lowers the alkalinity with it. Then aerate the water, with the returns aimed up at the surface or a waterfall or fountain running, so carbon dioxide escapes and the pH comes back up without the alkalinity coming back with it. Repeat until the alkalinity is in range. It takes a few days, and that is normal.
Pour acid slowly in front of a return with the pump running, and never let it meet chlorine. The CDC says to keep pool chemicals from mixing.
Can you lower alkalinity without lowering pH?
Not directly. Anything that lowers alkalinity lowers the pH with it. The trick is the aeration step, which brings the pH back up by itself while the alkalinity stays down.
Why does my alkalinity keep dropping?
Acid. Every dose of muriatic acid or dry acid that holds the pH down also eats a little alkalinity, and salt pools and new plaster push the pH up, so they tend to get a lot of acid. Heavy rain dilutes it too. Test alkalinity every week or two and top it up a little at a time. Or hand the testing off: on our weekly pool service the water gets tested and corrected every week, and the chemicals are part of the monthly price.
Does high alkalinity cause cloudy water?
It can. High alkalinity drags the pH up, and high pH makes calcium come out of the water as haze and scale. See why is my pool cloudy and how to remove calcium from pool tile.
Quick answers
- Should I adjust alkalinity or pH first?
- Alkalinity first. It sets how easily the pH moves, so once alkalinity is in range the pH is far easier to adjust and hold.
- Is soda ash the same as baking soda?
- No. Soda ash (sodium carbonate) raises the pH a lot and alkalinity some. Baking soda (sodium bicarbonate) raises alkalinity a lot and the pH a little. Soda ash is for low pH, baking soda is for low alkalinity.
- Can you swim after adding baking soda to a pool?
- Once it has dissolved and circulated, as long as the pH and chlorine are in range. Check the label of whatever you added for its own wait time.
Sources
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