Total Alkalinity Adjustment Formula
The Formula
Sodium bicarbonate (oz) = Desired TA Increase (ppm) × Volume (gal) × 0.0012
| Symbol | Description | Unit |
|---|---|---|
TA Increase | Target TA minus current TA in ppm | ppm |
Volume | Pool volume in gallons | gallons |
0.0012 | Pounds of sodium bicarbonate needed per ppm per gallon | lbs/ppm/gal |
Worked Example
Example
Pool: 18,000 gallons. Current TA: 60 ppm. Target TA: 100 ppm.
- TA increase needed = 100 − 60 = 40 ppm
- Dose = 40 × 18,000 × 0.0012
- Dose = 40 × 21.6 = 864 oz... let's convert
Using the simpler rule: 1.5 lbs per 10,000 gal per 10 ppm: - For 40 ppm increase: 1.5 × 4 = 6 lbs per 10,000 gal - For 18,000 gal: 6 × 1.8 = 10.8 lbs
Add approximately 10–11 lbs of sodium bicarbonate. Split into two additions if needed, waiting 4–6 hours between tests.
How This Formula Works
Total alkalinity (TA) is the pool's buffering capacity — it resists pH changes. Low TA causes pH to swing wildly with minor additions. High TA makes it difficult to lower pH.
- To raise alkalinity: sodium bicarbonate (baking soda). 1.5 lbs per 10,000 gallons raises TA by approximately 10 ppm.
- To lower alkalinity: muriatic acid. Adding acid lowers both pH and alkalinity. To specifically lower TA without driving pH too far down, add acid with the pump off, then aerate to bring pH back up.
- The 0.0012 constant is equivalent to 1.5 lbs raising TA by 10 ppm in 10,000 gallons.
Limitations & Notes
Sodium bicarbonate also causes a slight pH increase — usually 0.1 to 0.2 pH units for typical doses. Recheck and adjust pH after alkalinity correction if needed. TA should be stabilised before making pH adjustments.
Last reviewed: 2026-06-01