How much baking soda to raise alkalinity?
Plain sodium bicarbonate — the same compound in the orange box — is the alkalinity tool, and the dose math is mercifully linear: about 1.4 pounds raises 10,000 gallons by 10 ppm. Scaled out:
| Raise TA by | 10,000 gal | 15,000 gal | 20,000 gal |
|---|---|---|---|
| 10 ppm | 1.4 lb | 2.1 lb | 2.8 lb |
| 20 ppm | 2.8 lb | 4.2 lb | 5.6 lb |
| 30 ppm | 4.2 lb | 6.3 lb | 8.4 lb |
Verified against the calculator above, which handles any volume and any raise. Broadcast it over the deep end with the pump running; it dissolves in minutes. Retest after a few hours of circulation.
Check the label on the pool-store bucket: sodium bicarbonate, 100%. It's the identical compound sold in the baking aisle for a third of the price — a 13.5 lb resealable bag of food-grade baking soda treats a typical pool all season. This is one of the few pool chemicals where the generic isn't just as good; it's the same thing.
Alkalinity vs pH: which do you fix first?
They're two readings of one carbonate system — every dose that moves one nudges the other. The order that avoids chasing your tail: fix TA first when it's low (baking soda raises TA a lot and pH a little, and a properly buffered pool holds whatever pH you set next), and fix pH first when TA is high (acid lowers both, so you're making progress on two problems with one dose). The pH calculator shows the TA side effect of every acid and soda ash dose for exactly this reason.
How to lower alkalinity in a pool
Here's the answer most sites bury: there is no alkalinity-decreaser product. Anything sold under that name is just acid. Lowering TA is a two-step cycle you repeat:
1. Acid converts the buffer. Dose muriatic acid to pull pH down to 7.0–7.2. That converts bicarbonate into dissolved CO₂ — your TA is now lower, but the CO₂ is still in the water pushing pH down. 2. Aeration blows it off. Point returns at the surface, run a fountain, waterfall or robot — as CO₂ off-gasses, pH floats back up without raising TA. When pH reaches ~7.6, dose acid again. Each cycle shaves 10–20 ppm; a badly high pool takes a weekend or two of cycles, not one heroic dose.
TA at 100 with a stable pH is not a problem worth a weekend of acid cycles — the number that matters is whether your pH holds. Lower TA deliberately when pH climbs relentlessly, when the CSI shows scaling, or when your fill water is so alkaline the problem compounds every top-up. Otherwise, log it and move on.
What alkalinity actually does
TA is your water's shock absorber. Too low (under ~50) and pH lurches with every rainstorm, swimmer load and chlorine dose — the classic "my pH won't stay put" pool. Too high (over ~110) and the buffer itself becomes the problem: it drags pH upward continuously, forces you into an acid-dosing routine, and raises the scaling side of the saturation index. The 60–90 band is where the buffer works for you instead of against you. If your fill water runs high-TA (common across the Southwest and anywhere on well water), expect a slow upward drift every season — that's topping-up water bringing its own buffer along, not something you did wrong.