Baking soda vs soda ash: which one do you need?
Both are white powders that raise something in your pool. Both get tossed around in pool advice as if they're interchangeable. They're not. Baking soda raises alkalinity. Soda ash raises pH. Using the wrong one doesn't just fail to fix the problem — it makes your water chemistry worse.
What each one does
Baking soda (sodium bicarbonate) primarily raises total alkalinity (TA) with only a minimal effect on pH. Use it when your alkalinity is low but your pH is already in range. You can buy it at any grocery store — it's the same stuff in the orange box.
Soda ash (sodium carbonate) primarily raises pH, and it also raises alkalinity as a secondary effect. Use it when your pH is low. It's sold at pool supply stores, sometimes labeled "pH increaser" or "pH up."
Side-by-side comparison
| Baking Soda | Soda Ash | |
|---|---|---|
| Chemical name | Sodium bicarbonate | Sodium carbonate |
| Primary effect | Raises alkalinity | Raises pH |
| Secondary effect | Slight pH increase | Also raises alkalinity |
| When to use | Low TA, pH is fine | Low pH |
| Dosing | ~1.5 lbs per 10,000 gal raises TA ~10 ppm | ~6 oz per 10,000 gal raises pH ~0.2 |
| Dissolves | Quickly | Quickly (can cloud water briefly) |
| Cost | Very cheap (grocery store) | Moderate (pool supply) |
The common mistake
The most frequent error pool owners make is using baking soda to raise pH. It seems logical — baking soda is cheap, easy to find, and the internet is full of advice telling you to dump it in. But baking soda barely moves pH. Its main job is raising alkalinity.
If your pH is 7.0 and you add baking soda, your pH will barely budge while your alkalinity climbs well above range. Now you have a new problem: high TA that's going to keep pushing your pH up later and make it hard to control.
The simple rule
If your pH is low, you need soda ash. If your alkalinity is low, you need baking soda. Don't use one to do the other's job.
Decision guide
| Your Readings | What to Add | Why |
|---|---|---|
| pH low + TA low | Soda ash first | It raises both pH and TA at the same time |
| pH fine + TA low | Baking soda | Raises TA without significantly affecting pH |
| pH low + TA fine | Soda ash (small dose) | Raises pH; watch TA since it will rise too |
| pH high + TA high | Neither — you need acid | Muriatic acid or dry acid to bring both down |
Why order matters
When both pH and alkalinity are low, it's tempting to reach for baking soda first since it's cheaper. But that's the wrong move. Soda ash raises both pH and alkalinity, so it solves two problems at once. If you start with baking soda, you'll raise TA but pH will still be low — and then when you add soda ash to fix pH, you'll push TA even higher.
The correct order: always address pH first with soda ash. After pH is in range, retest alkalinity. If TA is still low, then add baking soda to bring it up the rest of the way.
How to add each one
- Pre-dissolve in a bucket of pool water before adding to the pool. This prevents clumping and ensures even distribution
- Add near a return jet with the pump running so it circulates quickly throughout the pool
- Wait at least 30 minutes before retesting. Give the water time to fully mix and the chemistry to stabilize
- Don't add both on the same day. Adjust one, retest, then decide if you still need the other. Adding both at once makes it impossible to know what moved what
Dosing tip
Always start with less than you think you need. It's much easier to add more of either chemical than to correct an overshoot. Add half the calculated dose, wait an hour, retest, and add more if needed.
Know exactly what to add
PoolChem Tracker tells you whether you need baking soda or soda ash — and exactly how much — based on your current readings and pool size.
Keep reading
- How to Lower Pool Alkalinity — when TA is too high and won't come down
- Pool pH Too High? Here's How to Fix It — safe ways to bring pH back into range
- How to Balance Pool Water in 4 Steps — the right order for adjusting all your levels
- Pool Chemistry for Beginners — the 5 numbers every pool owner should know