Baking soda is the answer
Raise total alkalinity with sodium bicarbonate, which is plain baking soda, the exact same thing sold as pool alkalinity increaser for more money. The amount depends on your pool volume and how far alkalinity needs to climb; the alkalinity calculator gives the dose. Aim for 80 to 120 ppm.
Add it dissolved in a bucket of pool water, or broadcast it slowly across the surface, with the pump running. Wait about six hours for it to circulate, then retest before adding more.
It nudges pH up a little too
Baking soda mainly raises alkalinity, but it will lift pH slightly as well. That is usually fine, since low-alkalinity pools often have low pH too. After the alkalinity settles, check pH with the pH calculator and fine-tune it into the 7.4 to 7.6 range if needed.
If you need a big pH jump without much alkalinity change, that is a job for soda ash or aeration instead, but for raising alkalinity, baking soda is the right tool.
Set alkalinity before pH
Always bring alkalinity into range first, then handle pH. Because alkalinity buffers pH, trying to dial in pH while alkalinity is low is a losing game; pH just drifts again. Get alkalinity to target, let it stabilize, and pH becomes far easier to hold.
Not sure of your pool volume? The pool volume calculator gives the gallons every dose depends on.
Why alkalinity drops
Total alkalinity falls over time from acidic rain, certain chlorine types like trichlor tablets, and simply adding acid to manage pH. Heavy rain and topping off with low-alkalinity fill water dilute it too.
If you keep landing low, recheck after each big rain and after any acid additions, since those are the usual culprits. A steady alkalinity in range is what keeps the rest of the chemistry calm.
Frequently asked questions
How do I raise alkalinity in a pool?
Add sodium bicarbonate, which is baking soda. The amount depends on your pool volume and how far alkalinity needs to rise, which the alkalinity calculator works out. Add it with the pump running, wait a few hours, and retest. Pool alkalinity increaser is the same chemical, usually for a higher price.
How much baking soda raises pool alkalinity?
About 1.4 pounds of baking soda per 10,000 gallons raises total alkalinity by roughly 10 ppm. Use the alkalinity calculator to scale that to your exact volume and target. Add it in stages and retest rather than dumping the whole amount at once.
Will baking soda raise pool pH?
A little. Baking soda mainly raises total alkalinity but does nudge pH up slightly. If you need a larger pH increase on its own, use soda ash or aerate the water. For raising alkalinity specifically, baking soda is the correct choice.
What should pool alkalinity be?
80 to 120 ppm for most pools. Total alkalinity is the buffer that holds pH steady, so set it into range first, then fine-tune pH. Some people aim a little lower, around 70 to 90, if they struggle to keep pH from drifting up.
Why does my pool alkalinity keep dropping?
Acidic rain, trichlor chlorine tablets, and adding acid to manage pH all lower alkalinity over time, as does diluting with low-alkalinity fill water. Recheck alkalinity after heavy rain and after acid additions, since those are the common reasons it falls out of range.