Quick Reference
Table of Contents
What It Does
Soda ash raises pH, and it raises total alkalinity at the same time. That second part is what people forget.
The cleanest way to think about it: for the same pH correction, soda ash moves TA less than baking soda would. For the same TA correction, soda ash overshoots pH badly. So soda ash is the pH tool and baking soda is the alkalinity tool, and picking the wrong one means fixing one number while wrecking the other.
Which Product Do You Actually Need
| Your Water | Reach For |
|---|---|
| pH low, TA low | Baking soda. Fixes TA and nudges pH up on the way |
| pH low, TA fine | Soda ash, or aerate |
| pH low, TA already high | Aerate. Soda ash here pushes TA further up |
| pH fine, TA low | Baking soda |
| pH high | Muriatic acid |
If your calcium hardness is high and the water already leans scale-forming, go easy on soda ash regardless of what the table says.
Try Aeration First
pH climbs on its own in most pools. Point a return jet up at the surface, run a fountain or waterfall, turn on the spa jets. That drives off carbon dioxide and raises pH while leaving TA alone.
It adds nothing to your water. Depending on how you do it, it may cost you some pump runtime, but nothing goes in that you later have to dilute out.
If pH keeps falling, find the cause. Usual suspects: trichlor tablets, an automated acid feeder, heavy manual acid use, or a lot of rain. Chasing it with soda ash forever means TA ratchets up every single time. Note that a saltwater generator usually pushes pH the other way, up, not down.
How to Add It
- Test both pH and TA before you pick a product.
- Use a calculator for the dose, add about three quarters of it, then retest.
- Pre-dissolve in a bucket of warm water. Chemical into water, never water into chemical. Gloves and eye protection.
- Add slowly in front of a return with the pump running, moving as you pour.
- Do not dump it in one spot. A concentrated slug spikes local pH high enough to drop calcium out of solution.
- Retest after 30-60 minutes of good circulation.
Why It Clouds Water
High pH plus dissolved calcium equals calcium carbonate falling out of solution. Same chemistry as scale, except suspended in the water instead of stuck to the wall.
Pools with high calcium hardness are the most prone, and adding too fast or in one spot is what triggers it. Pre-dissolving and broadcasting slowly mostly prevents it.
Borax as an Alternative
Borax raises pH with less effect on TA than soda ash. If TA is at the top of the range and pH is low, it is the cleaner tool. It leaves borates behind, which buffer against pH drift and have a mild algae-inhibiting effect around 30-50 ppm.
Borate cautions. Borates are not a sanitizer and will not replace chlorine. They are harmful if swallowed in quantity, which matters if you have a dog that drinks from the pool. Some areas restrict borate discharge, so check local rules before draining. If you are targeting a specific ppm, boric acid gets you there with far less pH disruption than borax, which needs acid to offset the rise.
Spas
Small volume, small doses. Pre-dissolve, add a little, retest.
Most spa owners rarely need soda ash. The jets aerate constantly, so spa pH tends to climb on its own and acid is the more common reach.
Trouble Free Pool has thorough write-ups on the acid and aeration cycle if you want the deeper version.