Total alkalinity: how much baking soda to add
Total alkalinity is the buffer that keeps pH steady. Here is how much baking soda it takes to raise it.
Safety: dosing figures are estimates. Follow the product label, add one chemical at a time, never mix pool chemicals, add chemical to water (never water to chemical), keep chemicals away from children, and re-test before swimming. Add about ¾ of a dose, re-test, then top up. Not a substitute for professional pool service.
Total alkalinity (TA) measures the carbonates and bicarbonates dissolved in your water — the compounds that absorb acid and base and keep pH from swinging. Get TA right and pH becomes easy to hold; get it wrong and pH will drift no matter how much acid or soda ash you chase it with. The everyday tool for raising TA is ordinary sodium bicarbonate — baking soda.
The formula
The standard increment is about 1.5 lb of baking soda per +10 ppm per 10,000 gallons, which scales cleanly:
pounds of baking soda = 1.5 × (Δppm ÷ 10) × (gallons ÷ 10,000)
Δppm is how much you want TA to rise. Because baking soda raises alkalinity strongly while nudging pH only slightly upward, it is the preferred way to lift TA without sending pH out of range.
Worked example
Raise a 15,000-gallon pool by 20 ppm:
1.5 × (20 ÷ 10) × (15,000 ÷ 10,000) = 1.5 × 2 × 1.5 = 4.5 lb of baking soda.
Scale it any way you like: +10 ppm in a 20,000-gallon pool is 1.5 × 1 × 2 = 3 lb; +30 ppm in a 10,000-gallon pool is 1.5 × 3 × 1 = 4.5 lb.
What range to aim for
Most pools are kept around 80–120 ppm total alkalinity, with plaster and gunite pools often toward the higher end and vinyl or fiberglass a little lower. Check what suits your surface and your generator. The point of the range is stability: within it, pH resists the daily push and pull of bathers, rain, chlorine and aeration.
Raising vs lowering TA
To raise TA: add baking soda as above, with the pump running, broadcast across the surface, and re-test after a full circulation cycle. To lower TA: you add acid (muriatic or dry), which lowers both alkalinity and pH — you then aerate to bring pH back up while alkalinity stays down. Lowering alkalinity is inherently an estimate and usually takes more than one pass, so go gradually.
Alkalinity and pH work together
Think of alkalinity as the coarse adjustment and pH as the fine one. Set TA into range first with baking soda, then dial pH to about 7.4–7.6 with acid or soda ash. If you find yourself constantly correcting pH, your alkalinity is probably off — fix the buffer and the pH follows. High alkalinity, in particular, tends to drag pH upward and cause scaling, so do not overshoot when adding baking soda.
How alkalinity, pH and calcium balance together
Total alkalinity is one leg of a three-legged stool — alkalinity, pH and calcium hardness — that together, along with water temperature, decide whether your water is balanced, scale-forming or corrosive. This is the idea behind the saturation (Langelier) index pool pros use: no single reading tells the whole story. High alkalinity and high calcium with a high pH tip water toward scaling, leaving cloudy water and crusty deposits on tile and heater elements. Low alkalinity with low pH tips it toward corrosion, etching plaster and attacking metal. Keeping all three in their ranges keeps the water clear and your surfaces intact.
Start from your fill water
Where you begin depends on what comes out of the hose. Some municipal and well water is naturally high in alkalinity, so a fresh fill or a big top-up can lift your reading before you add anything; other sources are soft and low. Test the pool a day or two after a large water change and correct from there. Because baking soda raises alkalinity strongly with only a small pH bump, it is the tool for lifting a low reading, while lowering a high one means adding acid and then aerating the pH back up — a slower, estimate-driven process best done in stages. Adjust alkalinity as the coarse control, then fine-tune pH, and the pair will hold steady far longer.
The bottom line
Total alkalinity is the buffer that makes pH manageable, so treat it as your coarse adjustment and set it first. Raising it is easy and predictable: about 1.5 pounds of baking soda per 10 ppm per 10,000 gallons, scaled to your pool. Aim for a range around 80 to 120 ppm, tuned to your surface and generator, then fine-tune pH on top. Lowering alkalinity is the harder direction — it means adding acid and aerating the pH back up over several gradual passes — so avoid overshooting when you add baking soda. Test after any large water change, since your fill water carries its own alkalinity. Get this buffer right and pH stops fighting you; keep chasing pH and the real fix is almost always here, in the alkalinity.
Compute your exact baking-soda dose on the alkalinity calculator, then fine-tune with the pH calculator and keep an eye on calcium hardness to avoid scale.