What is the difference between soda ash and baking soda?
The difference is which reading each one moves. Soda ash (sodium carbonate) mainly raises pH, while baking soda (sodium bicarbonate) mainly raises total alkalinity. They are chemically close, carbonate versus bicarbonate, but they behave differently in the water because of how alkaline each one is on its own.
Soda ash is strongly alkaline. Its own solution sits around pH 11.4, so a modest dose drags pool pH up fast, which is why it is sold as pH Up or pH Increaser. It raises total alkalinity somewhat as a side effect, but its real job is pH. Use it when pH is below the 7.4 to 7.6 target but your alkalinity is already in range. Size the amount with the pool pH calculator and follow the how to raise pH guide.
Baking soda is only mildly alkaline. Its solution sits around pH 8.3, which happens to be near where you want pool water to settle, so it raises total alkalinity strongly while nudging pH up only a little. It is the same sodium bicarbonate as the kitchen box, just cheaper in a big bag, and pool brands sell it as Alkalinity Increaser. Use it when total alkalinity is below the 80 to 120 ppm range. The how to raise alkalinity guide and the pool alkalinity calculator cover the dose.
Which one raises pool pH, soda ash or baking soda?
Soda ash is the one that raises pH meaningfully; baking soda only bumps it up a little. If your pH is low and you want it up, soda ash is the tool.
Because soda ash's own solution is so alkaline, around pH 11.4, a small amount moves pool pH up quickly. Baking soda's solution tops out near pH 8.3, so it can only carry pool pH so far. Adding extra baking soda will not push pH into the high 7s the way soda ash does; it just keeps building alkalinity. That ceiling is a feature, not a flaw, because it is what makes baking soda so hard to overshoot.
The catch with soda ash is the opposite: it is easy to overshoot and cloud the water. Add it pre-dissolved in a bucket, in stages, with the pump running, then circulate and retest before adding more, because high pH clouds a pool and starts scale forming. If pH is only slightly low, you can skip the chemical entirely; aerating the water, by running the returns pointed up or a fountain, raises pH for free. Size any dose with the pool pH calculator.
Which one raises total alkalinity?
Baking soda is the alkalinity raiser. It pushes total alkalinity up strongly while barely touching pH, which is exactly what you want when alkalinity is low but pH is fine.
Total alkalinity is the water's buffer, the thing that keeps pH from bouncing around. When it drops below 80 ppm, pH gets unstable and swings on you. Baking soda is the standard fix, and because it moves pH so gently, you can raise alkalinity back into range without knocking pH out of it. Soda ash also raises alkalinity, but it raises pH far more aggressively at the same time, so it is the wrong tool when only alkalinity is low.
Baking soda is forgiving. Too much only overshoots alkalinity above the 120 ppm ceiling, which you can pull back down later with acid; it will not spike pH the way excess soda ash can. Even so, add it in stages, circulate, and retest. One exception: if your alkalinity is already high and only pH is low, do not reach for either powder. That situation calls for the aerate-and-acid method in the how to lower alkalinity guide.
Soda ash or baking soda: which should you use?
Pick by which reading is low. Alkalinity low, use baking soda. pH low with alkalinity fine, use soda ash. Both low, start with baking soda.
The both-low case is the common one, and it trips people up. Fix alkalinity first with baking soda, because raising alkalinity usually carries pH up along with it. Circulate, retest, and only then add soda ash if pH is still below 7.4. Doing it the other way, soda ash first, often overshoots pH while alkalinity is still low and unstable, so pH will not hold and you end up dosing twice. The right order is alkalinity before pH; our how to balance pool water guide walks the full sequence.
If you are deciding what to keep in the shed, baking soda is the one you will reach for most, since alkalinity drifts down over time from rain, dilution, and acidic sanitizers, and steady alkalinity is what keeps pH from wandering. Keep soda ash on hand too for the times pH alone sags. Both are cheap. Check your targets against the ideal pool chemistry levels and size any dose with the pool volume calculator plus the pool pH or alkalinity calculator.
Soda Ash wins on
- +Raises pH fast and far; the only one of the two that lifts pH into the mid to high 7s.
- +The right tool when pH is low but total alkalinity is already in range.
- +A little goes a long way, so a small tub lasts a long time.
Baking Soda wins on
- +Raises total alkalinity strongly while barely moving pH, so it steadies the water without overshooting.
- +Very forgiving; too much only overshoots alkalinity, which is easy to correct with acid.
- +The everyday product, since alkalinity is the reading that drifts down most and needs topping up most often.
The verdict
There is no single winner, because they fix different readings, but they are not interchangeable, and treating them as the same product is the mistake to avoid. Use baking soda (sodium bicarbonate) to raise total alkalinity when it drops below 80 ppm; it barely moves pH, so it steadies the water without overshooting. Use soda ash (sodium carbonate) to raise pH when pH is low but alkalinity is already in the 80 to 120 ppm range; it is the only one of the two that lifts pH meaningfully, so add it dissolved, in stages, with the pump running, and retest before adding more, because it clouds water and scales if you overshoot. When both are low, which is the usual case, start with baking soda and let it carry pH up with the alkalinity, then add soda ash only if pH is still short of 7.4. If you can keep only one on hand, keep baking soda, because alkalinity is the reading that drifts down most. Balance alkalinity before pH, size every dose with the pool pH calculator or pool alkalinity calculator, and follow the order in our how to balance pool water guide.
Related: Pool pH calculator, Pool alkalinity calculator, How to raise alkalinity.
Frequently asked questions
Can I use baking soda in place of soda ash?
Not really, because they do different jobs. Baking soda raises total alkalinity and nudges pH up only a little, while soda ash raises pH strongly. If your pH is low and you substitute baking soda, you will raise alkalinity but barely move pH, and if alkalinity is already high you will push it out of range. The reverse fails too: using soda ash to fix low alkalinity will spike pH. Match the product to the reading that is low, and size it with the pool pH calculator or pool alkalinity calculator.
What raises pool pH quickly?
Soda ash (sodium carbonate), sold as pH increaser, raises pool pH the fastest. Its solution is strongly alkaline, so a small dose moves pH up quickly. Add it pre-dissolved and in stages with the pump running, then retest, because it is easy to overshoot and cloud the water. If pH is only slightly low, aerating the water (running the returns pointed up or a fountain) raises pH for free with no chemical. Baking soda raises pH only slightly, so it is not the quick fix for low pH. Size the dose with the pool pH calculator.
How much soda ash does a 10,000 gallon pool need?
It depends on how far below target your pH is, so there is no single number. Test pH first, then size the exact amount for your pool volume and current reading with the pool pH calculator. Add it in stages, dissolved in a bucket of water and poured in with the pump running, then circulate and retest before adding more, because soda ash raises pH fast and overshooting clouds the water and can start scale forming. Do not eyeball a whole pool's worth at once.
What happens if you put too much baking soda in a pool?
Too much baking soda overshoots total alkalinity above the 120 ppm ceiling, which makes pH stubborn and prone to drifting high, and very high alkalinity can cloud the water and encourage scale. It will not spike pH the way excess soda ash can, so baking soda is forgiving, but overshooting still means extra work. Bring high alkalinity back down with the aerate-and-acid method in our how to lower alkalinity guide. Add baking soda in stages and retest to avoid the problem in the first place.
When should you add soda ash instead of baking soda?
Add soda ash when pH is low (below about 7.4) but total alkalinity is already in the 80 to 120 ppm range, so you only need to move pH. Add baking soda when total alkalinity is low, whether or not pH is low, because it fixes alkalinity and gently lifts pH too. When both are low, add baking soda first, circulate and retest, then add soda ash only if pH is still short. Give either chemical a few hours of circulation before you retest so the reading is true. See the full order in our how to balance pool water guide.