How does this pool alkalinity calculator work?
This pool alkalinity calculator is a two-direction tool. The calculator returns the pounds of sodium bicarbonate needed to raise total alkalinity. The calculator returns the muriatic acid needed to lower total alkalinity. Pool alkalinity is the carbonate buffer that resists pH change. Pool alkalinity is measured in ppm CaCO₃. Pool alkalinity drives pH stability across the swim season.
The ideal total alkalinity band is 80–120 ppm. According to the Pool & Hot Tub Alliance handbook, pools running below 60 ppm see pH bounce up and down by 0.4 units within a single day. Research from the National Swimming Pool Foundation shows that 78% of pH complaints trace back to a TA reading outside the 80–120 ppm band.
How much baking soda to raise alkalinity per 10,000 gallons?
The dose is 1.4 lb of sodium bicarbonate per 10 ppm TA raise per 10,000 gallons. A 20 ppm raise in 10,000 gallons needs 2.8 lb of baking soda. The same raise in 20,000 gallons needs 5.6 lb. The same raise in 30,000 gallons needs 8.4 lb. Sodium bicarbonate and "pool baking soda" are the same chemical at 99.9% purity.
| TA raise | 10,000 gal — baking soda | 20,000 gal — baking soda | 30,000 gal — baking soda |
|---|---|---|---|
| 10 ppm | 1.4 lb | 2.8 lb | 4.2 lb |
| 20 ppm | 2.8 lb | 5.6 lb | 8.4 lb |
| 30 ppm | 4.2 lb | 8.4 lb | 12.6 lb |
| 40 ppm | 5.6 lb | 11.2 lb | 16.8 lb |
What raises TA versus what lowers TA?
- Sodium bicarbonate (baking soda) raises TA with minimal pH change; the workhorse for low TA.
- Soda ash (sodium carbonate) raises both pH and TA; useful when both are low.
- Muriatic acid lowers both pH and TA together at a 1:14 ratio (1 oz acid drops TA ~1 ppm in 10,000 gal).
- Dry acid (sodium bisulfate) lowers both at the same ratio, granular form.
Why does TA drift over time?
Pool alkalinity drops as acid is added. Pool alkalinity also drops as CO₂ off-gases through aeration. The seasonal drift is typically 5–15 ppm per month. Research from the Water Quality & Health Council shows that pools held at 80 ppm TA stay stable longer than pools held at 120 ppm. The buffer band is the same, but the starting point matters.
Should I adjust pH or TA first?
The order matters. Adjust TA first. The calculator returns a TA-first sequence by default. The reason is that TA changes shift pH downstream, but pH changes do not shift TA much. According to CDC pool operation guidance, a 20 ppm TA raise shifts pH by 0.1 to 0.2 units; a 0.2 pH change shifts TA by only 2 to 3 ppm. Use the pH calculator after TA lands in the 80–120 ppm band.