Total alkalinity (TA) is the pH shock absorber. Without it, your pH bounces every time something enters the water — rain, a swimmer, a chemical dose. With it, pH stays stable and your life gets a whole lot easier.
Target range: 80 – 120 ppm. Some pros prefer the low end (80–100) to reduce pH drift-up in outdoor pools.
How TA and pH interact
If TA is too low, pH reacts wildly to every dose and every storm. If TA is too high, pH locks in at a stubbornly high value (usually 7.8+) that resists acid additions — and the acid you add kills the alkalinity before it moves pH. This is called pH bounce vs. pH lock, and both are miserable.
How to raise total alkalinity
Use sodium bicarbonate (baking soda). It's cheap, safe, and barely moves pH.
Dosing (10,000-gallon pool): 1.5 lb baking soda raises TA by ~10 ppm. Broadcast across the deep end with pump running. Wait 6 hours, retest.
How to lower total alkalinity
This is trickier. You can't directly remove TA without lowering pH first. The “slug method” is:
- Turn off pump (no circulation).
- Add muriatic acid slowly into the deepest point — a concentrated “slug.”
- Wait 1 hour with pump still off so the acid reacts with bicarbonate in place.
- Turn pump back on and aerate to raise pH back up (fountain, waterfall, jets pointed up).
- Repeat until TA is in range.
What messes with TA
- Rain dilutes alkalinity and pushes pH down.
- Acid additions eat TA (1 lb muriatic acid removes ~6 ppm TA).
- Baking soda raises both TA and pH slightly.