Soda Ash vs Baking Soda for a Pool: Doses Compared

Side by side in 15,000 gal (pH 7.4 now)
Goal	Baking soda (sodium bicarbonate)	Soda ash (sodium carbonate)
Raise TA by 10 ppm	2.1 lb → pH about 7.44	1.35 lb → pH about 7.87
Raise pH by 0.2	12.7 lb, TA +60 ppm	11.0 oz, TA +5.2 ppm

Both are white powders, both are sold for pools under several names, and both raise pH and alkalinity a little. The difference is how much of each they move. The calculator above runs both products through the same water model as our pH and alkalinity calculators and puts the results side by side. Enter your gallons, pH, total alkalinity (TA), and stabilizer (CYA).

Which one do you need?

Pick the product by your test results
Your test	Use	Why
TA below 80 ppm, pH fine or low	Baking soda	Raises TA with only a small pH change
pH below 7.4, TA in range	Soda ash	Raises pH with only a small TA change
pH and TA both low	Baking soda first, then retest	Raising TA lifts pH a little; add soda ash only if pH is still low
TA low, pH high	Baking soda, then lower pH with acid	Soda ash would push pH even higher

The ranges come from our targets: pH 7.4–7.6 and TA 80–120 ppm for most pools. The CDC's wider pH range for home pools is 7.0–7.8. See pH vs alkalinity if you are not sure which number is the problem.

Side by side: the same goal with each product

The calculator's example is a 15,000-gallon pool at pH 7.4, TA 80 ppm, and CYA 30 ppm. It shows what happens if you use each product for each goal:

Raise TA by 10 ppm. Baking soda: 2.1 lb, and pH ends up about 7.44. Soda ash: 1.35 lb, but pH jumps to about 7.87.
Raise pH by 0.2. Soda ash: 11 oz, and TA rises only about 5.2 ppm. Baking soda: 12.7 lb, and TA climbs about 60 ppm on the way.

So each product is the efficient choice for one job and a poor choice for the other. Soda ash used to fix low alkalinity overshoots pH. Baking soda used to fix low pH takes a lot of product and can leave TA too high. These are model estimates, so add part of the dose, run the pump, and retest. Always follow the product label.

Why they behave differently

Both are sodium salts of carbonic acid. Baking soda is bicarbonate, the same form most of your alkalinity is already in, so it adds alkalinity without shifting the balance much. Soda ash is carbonate, a stronger base: it turns some bicarbonate into carbonate, and that raises pH quickly. The numbers show the gap: a 1% soda ash solution has a pH of about 11.4 (HASA safety data sheet), while a baking soda solution is about 8.3 (PubChem).

That is also why, if TA is low, pH drifts back down after you raise it with soda ash: there is not enough alkalinity (buffer) to hold the new pH. Fix TA first, then fine-tune pH.

Cloudy water after soda ash

A white haze right after soda ash is usually calcium carbonate. Where the powder lands, pH rises very high for a moment, and calcium in the water comes out as fine particles. It is more likely in hard water, in warm water, or when you add a lot at once. Run the pump and keep the filter clean; the haze usually clears as the water mixes. To avoid it next time:

Dissolve the soda ash in a bucket of pool water first.
Pour it slowly across a wide area in front of a return jet.
Split a large dose into two or more parts, a few hours apart.

If the haze lasts more than a day or two, check your calcium hardness and pH with the LSI calculator, and see cloudy pool water.

How to add either one

Test pH and TA, and enter them in the calculator with your gallons.
Weigh the dose. Baking soda for TA is often several pounds; soda ash for pH is usually ounces.
With the pump running, broadcast baking soda over the water, or dissolve soda ash in a bucket of pool water first.
Add one product at a time. Wait at least 30 minutes with the pump running before the next chemical.
Retest after a few hours. Adjust in small steps rather than one big dose.

Doses for one product at a time are on how to raise alkalinity (baking soda) and how to raise pH (soda ash or borax).

Names on the bag: pH up, alkalinity up, washing soda

"pH up", "pH plus", or "pH increaser" is usually soda ash (sodium carbonate).
"Alkalinity up", "alkalinity plus", or "alkalinity increaser" is usually baking soda (sodium bicarbonate).
Grocery-store baking soda is the same sodium bicarbonate.
Laundry "washing soda" is sodium carbonate, the chemical in soda ash; PubChem lists both names for it. It is sold as a laundry product, not for pools, so if you use it, check that the box lists sodium carbonate and nothing else, such as fragrance.

Read the active ingredient, not the front of the bag. If it lists something else, such as borax, these doses do not apply.

Safety

Soda ash is strongly alkaline: wear gloves and eye protection, and don't breathe the dust. Never mix pool chemicals in the same bucket, and never add soda ash or baking soda at the same time as acid. Add chemicals to water, not water to chemicals. Store them dry, sealed, and out of children's reach. Poison Control: 1-800-222-1222. Always follow the product label.

FAQ

Can I use baking soda instead of soda ash?

Only if alkalinity is also low. Baking soda raises pH only a little per pound: in the example, raising pH by 0.2 takes 12.7 lb of baking soda and adds about 60 ppm of TA. If TA is already in range, soda ash is the better tool.

Can you raise alkalinity with soda ash?

Yes, but pH rises a lot with it. In the example, 1.35 lb of soda ash raises TA by 10 ppm and pushes pH from 7.4 to about 7.87. Baking soda does the same TA job with almost no pH change.

Can I add soda ash and baking soda on the same day?

Yes, one at a time. Add baking soda first, wait at least 30 minutes with the pump running, retest pH, and add soda ash only if pH is still low.

Why did my pool turn cloudy after soda ash?

Most likely calcium carbonate formed where the soda ash landed. Keep the pump running and the filter clean. Next time, dissolve it first and add it in smaller parts.

Sources

Doses and pH results: our engine's carbonate model (the same model as our pH and alkalinity calculators); see methodology.
CDC, Home pool and hot tub water treatment and testing (pH 7.0–7.8): cdc.gov
HASA, Soda ash safety data sheet No. 208 (pH 11.4 at 1%): PDF
PubChem, Sodium bicarbonate (pH 8.3 in a 0.1 molar solution): pubchem.ncbi.nlm.nih.gov
Orenda, Why does soda ash cloud up pool water? (secondary, maker blog): orendatech.com
PubChem, Sodium carbonate (synonyms include soda ash and washing soda): pubchem.ncbi.nlm.nih.gov
Taylor Technologies, Your pool's total alkalinity explained: taylortechnologies.com