Is Pool-Store 'Alkalinity Up' Just Baking Soda? (Pool & Hot Tub)
The myth You need a special pool-store 'Alkalinity Increaser' — plain baking soda isn't the same thing.
Pool and spa 'Alkalinity Increaser' / 'Alkalinity Up' is sodium bicarbonate — the exact same chemical as the baking soda in the grocery-store box, usually at several times the price. Baking soda raises Total Alkalinity (your pH buffer) with only a small nudge to pH, so reach for it when your TA is low, not when your pH is low (that's soda ash's job, or just run a water feature to aerate). Dose by your water volume — our calculator does the math — add about three-quarters, run the pump, and retest. In a hot tub it's the same chemistry in a fraction of the water: think ounces, not pounds, and expect the jets to push your pH up fast.
Walk into a pool store with low alkalinity and you’ll walk out with a bag of “Alkalinity Increaser.” Flip it over and read the ingredient: sodium bicarbonate. That’s baking soda. The same thing in the orange box at the grocery store, usually for a fraction of the price.
It’s the same chemical
Pool and spa products sold as “Alkalinity Increaser,” “Alkalinity Up,” or “Total Alkalinity Increaser” are 100% sodium bicarbonate — chemically identical to the baking soda you’d bake with. There’s no secret pool additive that makes the branded bag work better; a pound of it and a pound of grocery baking soda do exactly the same thing to your water.
The markup is the whole trick. A few pounds of “pool alkalinity increaser” can cost several times what the same weight of plain baking soda costs. Food-grade sodium bicarbonate dissolves and behaves identically in your pool — buy the cheap box.
What it actually does: raises alkalinity, not pH
Here’s the part that trips people up. Baking soda’s job is Total Alkalinity — the buffer that keeps your pH from swinging around. It barely touches pH itself (it only nudges pH toward about 8.3). So:
- Total alkalinity low? Baking soda (sodium bicarbonate). Raises TA, tiny pH bump.
- pH low, alkalinity OK? Soda ash (sodium carbonate, sold as “pH Up”) raises pH strongly — or just aerate the water, which raises pH with no TA change at all.
- pH high? That’s muriatic acid’s job, not either powder.
Reaching for baking soda to fix a low pH is the classic mistake — you’ll dump pounds in, watch pH barely move, and end up with sky-high alkalinity that makes your pH stubborn for weeks. Target TA is 60–80 ppm (see the 5 numbers); if you’re already in range, leave it alone.
How much, and how to add it
About 1.5 lb per 10,000 gallons raises TA ~10 ppm — but dose by your real volume and target with the dosing calculator rather than guessing. Then:
- Broadcast it across the deep end with the pump running (don’t pile it in one spot).
- Add about three-quarters of the calculated dose, circulate, wait, and retest before adding more. Overshooting TA is easy and annoying to walk back.
- A little temporary cloudiness is normal and clears in an hour or two.
In a hot tub or spa
Same chemical, a fraction of the water — so the doses shrink from pounds to ounces. In a typical 400-gallon spa, about one ounce (two tablespoons) of baking soda raises TA roughly 10 ppm, so add a little, run the jets to mix, and retest. Two spa-specific things to know:
- Your pH will climb fast. Spa jets aerate the water hard, and aeration drives pH up — so expect to add acid more often, while your alkalinity does the buffering. Keeping TA in range is what keeps that pH climb slow and manageable.
- Skip the “spa alkalinity increaser” too. It’s the same sodium bicarbonate as the pool version and the grocery box. In a small spa the price gap on a tiny amount is minor, but the chemistry is identical — a spoon of plain baking soda does it.
The honest bottom line
There is no magic in the pool-store bag. “Alkalinity Increaser” is baking soda, one of several things the pool store sells you that you don’t need in a special form. Use plain sodium bicarbonate when your TA is low, match it to the right number (TA, not pH), dose by volume, and don’t chase alkalinity that’s already in range. That’s the whole game — and it ties back to the same idea behind everything here: less is more.
Frequently asked
Is pool 'Alkalinity Increaser' the same as baking soda?
Yes. Pool and spa products labeled 'Alkalinity Increaser,' 'Alkalinity Up,' or 'Total Alkalinity Increaser' are sodium bicarbonate — the identical chemical to the baking soda in the grocery-store box, usually sold at several times the price. Plain baking soda does exactly the same job in your pool. There's no pool-specific additive that makes the branded version work better; it's the same compound.
Does baking soda raise pH or alkalinity in a pool?
Mainly total alkalinity, with only a small effect on pH. Baking soda (sodium bicarbonate) is the go-to when your TA is low. It nudges pH slightly toward about 8.3 but won't move a low pH much — so if your pH is what's low, baking soda is the wrong tool. For pH you want soda ash (sodium carbonate, sold as 'pH Up'), or simply aerate the water, which raises pH without touching alkalinity.
Baking soda or soda ash — which do I use?
Match the chemical to the number that's off. Total alkalinity low? Use baking soda (sodium bicarbonate) — it raises TA with a small pH bump. pH low but alkalinity fine? Use soda ash (sodium carbonate, 'pH Increaser'), which raises pH strongly and TA somewhat, or aerate to raise pH with no TA change. pH high? That's acid's job, not either powder. Reaching for the wrong one is why people chase their numbers in circles.
How much baking soda do I add to raise pool alkalinity?
Roughly 1.5 pounds of baking soda per 10,000 gallons raises total alkalinity about 10 ppm. Always dose by your actual water volume and target — our dosing calculator does the exact math for your pool. Add about three-quarters of the calculated amount, run the pump to circulate, wait, and retest before adding more; it's easy to overshoot, and a high TA makes your pH stubborn to move later.
Can I use baking soda in a hot tub or spa?
Yes — it's the same sodium bicarbonate, just in a fraction of the water, so think ounces instead of pounds. In a typical 400-gallon spa, roughly one ounce (about two tablespoons) raises total alkalinity around 10 ppm, so add a little, run the jets to mix, and retest. Expect spa pH to climb fast because the jets aerate hard, and the branded 'spa alkalinity increaser' is — you guessed it — baking soda too.
Will baking soda make my pool cloudy?
It can go briefly cloudy if you dump a lot in one spot, but it clears on its own. Broadcast it across the deep end with the pump running rather than piling it in, and the cloudiness settles in an hour or two as it dissolves and circulates. If your water stays cloudy after that, alkalinity wasn't the cause — look at chlorine and filtration.