Soda ash is the usual fix
The standard chemical for raising pH is soda ash, also called sodium carbonate. It raises pH quickly and is cheap and widely sold. The amount depends on your pool volume and how far pH needs to climb; the pH calculator gives the dose. Aim for a pH of 7.4 to 7.6.
Borax is another option some people use, but soda ash is the simplest and most common. Add it dissolved in a bucket of pool water, poured around the perimeter with the pump running, and retest after it circulates.
Aeration raises pH for free
Here is the trick most people miss: you can raise pH with no chemicals at all by aerating the water. Running fountains, spa jets, a waterfall, or a return pointed up toward the surface off-gasses carbon dioxide, and that pushes pH up on its own.
Aeration is the better choice when your total alkalinity is already where you want it, because soda ash raises alkalinity along with pH. If you only need pH up and not alkalinity, aerate instead of dosing.
Watch alkalinity while you do it
Soda ash raises total alkalinity as well as pH, so if your alkalinity is already on the high side, a chemical pH raise can push it too far. Check it with the alkalinity calculator and keep alkalinity in the 80 to 120 ppm range. This is the main reason aeration is so handy: it moves pH without touching alkalinity.
Why pH drops in the first place
Persistent low pH usually traces back to low total alkalinity, which lets pH swing and sink. Acidic rain, certain chlorine types like trichlor tablets, and overcorrecting with acid can all pull pH down too.
If pH keeps falling, raise total alkalinity into range first. With a healthy alkalinity buffer, pH holds far more steadily and you stop chasing it.
Frequently asked questions
What raises pH in a pool?
Soda ash, also called sodium carbonate, is the standard chemical that raises pH. Aeration, such as running fountains or jets to off-gas carbon dioxide, also raises pH with no chemicals. Use soda ash for a quick fix, or aerate when you want pH up without raising alkalinity.
Can I use baking soda to raise pool pH?
Not really for pH. Baking soda (sodium bicarbonate) mainly raises total alkalinity and barely nudges pH. To raise pH specifically, use soda ash (sodium carbonate) or aerate the water. Baking soda is the right tool for raising alkalinity, not pH.
How do I raise pH without raising alkalinity?
Aerate the water. Running fountains, spa jets, a waterfall, or a return pointed up off-gasses carbon dioxide and raises pH on its own, with no change to alkalinity. Soda ash works too but raises alkalinity along with pH, so aeration is better when alkalinity is already in range.
Why is my pool pH low?
Usually low total alkalinity, which lets pH sink and swing. Acidic rain, trichlor chlorine tablets, and overdosing acid can also pull it down. The lasting fix is to get total alkalinity into the 80 to 120 ppm range, which buffers pH and keeps it steady.
What is the ideal pool pH?
7.4 to 7.6. That range is comfortable for swimmers, keeps chlorine effective, and protects surfaces and equipment. Below about 7.2 the water turns corrosive; above 7.8 chlorine weakens and scale can form.