Total alkalinity is pH's shock absorber. When it's low, pH won't sit still — it swings on every rain, every dose, every splash. The fix is cheap and forgiving: baking soda. Here's how much to add and how to do it right.
Why low alkalinity makes pH bounce
Alkalinity (TA) is the water's buffer — the reserve that resists pH change. Drop it too low and there's nothing holding pH steady, so it lurches up and down and you end up chasing it with acid and base all week. Raising TA back into range is what makes pH stay where you put it.
The ideal range
Aim for 80–120 ppm total alkalinity on a standard chlorine pool. On a saltwater pool, run the low end — about 60–90 ppm — because the salt cell's aeration constantly pushes pH up, and lower TA keeps that drift manageable.
The dose: how much baking soda
The rule the calculator uses: about 1.5 lb of baking soda per 10,000 gallons raises TA roughly 10 ppm. So to lift a 20,000-gallon pool from 60 to 100 ppm (a 40-ppm bump) you'd add about 12 lb. Enter your own numbers for an exact figure. Alkalinity calculator →
Step by step
- Test first. Get a real alkalinity reading with a drop kit or strips so you know your starting point.
- Measure the dose for your volume — and round down. It's easy to add more baking soda later; you can't take it out.
- Broadcast it with the pump running. Sprinkle it across the surface over the deep end so the circulation carries it. No need to pre-dissolve.
- Let it circulate for a full turnover — several hours or overnight — before you test again.
- Re-test, then top up if you're still short. Two smaller doses beat one overshoot.
Baking soda vs. alkalinity increaser
They're the same chemical. "Alkalinity increaser" or "Alkalinity Up" is just packaged sodium bicarbonate at a markup — plain baking soda gives the identical result, usually for less. Always confirm the active ingredient on the label.
Baking soda vs. soda ash
Don't confuse the two. Baking soda (sodium bicarbonate) raises alkalinity with only a small nudge to pH — use it when TA is low. Soda ash (sodium carbonate) raises pH sharply — use that when pH is low but alkalinity is already fine. Reach for the wrong one and you'll overshoot pH. See the right order to balance →.