Pool Alkalinity Range: What TA Should Be and Why

Aim for 60–90 ppm instead if you use liquid chlorine, bleach, or a salt water generator and your pH keeps climbing. TA is the water's buffer: it slows pH swings, but the higher it is, the faster pH drifts up.

Target ranges and why lower TA can be better

Total alkalinity targets, ppm as calcium carbonate
Source or situation	TA
ANSI/APSP-11 acceptable range (as cited by PHTA)	60–180
Taylor Technologies "ideal"	80–120
Trichlor tablets as the main chlorine source	80–120 (tablets are acidic and use up TA)
Liquid chlorine, bleach, or salt water generator	60–90 (our option for less pH rise)
Plaster pool with low calcium	upper part of the range helps water balance

Why lower can be better: most of your alkalinity is bicarbonate, which comes with dissolved carbon dioxide. As carbon dioxide (CO2) escapes into the air, pH rises. Lower TA means less carbonate to feed that process, so pH climbs more slowly. Pools on liquid chlorine or salt cells have no acidic tablets pulling pH down, so they often need acid every few days at TA 120 and much less at TA 70. The trade-off is less buffer against sudden drops, so don't go below about 60 ppm.

TA vs pH

They are linked but not the same. pH is how acidic the water is right now. TA is how much acid it takes to move pH down, roughly the size of the buffer. Two pools can both read pH 7.5 while one has TA 60 and the other TA 140. Add the same cup of acid to each, and pH in the first pool drops much further.

Practical consequences:

Baking soda raises TA a lot and pH only a little. Soda ash raises pH a lot and TA less. See how to raise alkalinity.
Acid lowers both. Lowering TA without letting pH fall too low means adding acid and then aerating to bring pH back up. How to lower alkalinity explains the steps.
Taylor's rule is to bring TA into range before fine-tuning pH, because pH won't hold while TA is far off. Our order puts chlorine first when it is below the minimum; sanitizing comes before balance.

For how pH itself behaves, see pool pH levels.

Why it rises or drops

TA rises when you add bases that contain carbonate: baking soda, soda ash, and, to a small degree, borax. Topping up with hard, high-alkalinity tap or well water raises it as the pool evaporates, because the minerals stay behind. Fresh plaster can raise it during curing. Test your fill water once. If it reads 150 ppm, your pool will drift toward 150 ppm.

TA drops with every acid dose, with trichlor tablets (by calculation, about 0.7 ppm TA per 1 ppm of chlorine used; at 2 ppm of chlorine a day, that is roughly 10 ppm a week), with non-chlorine shock, and with rain, which dilutes the pool with water that has almost no alkalinity.

CYA correction (carbonate alkalinity)

A standard TA test counts every buffer in the water, including stabilizer (cyanuric acid, CYA). Part of what reads as "alkalinity" in a stabilized pool is actually cyanurate, which does not help balance calcium. For water balance (the LSI calculator), you need carbonate alkalinity:

Carbonate alkalinity ≈ TA − (CYA × a factor that depends on pH). Taylor's Watergram applies a cyanurate correction. A common shortcut is to subtract about one-third of the CYA reading at typical pH. Our calculator works out the factor from the chemistry (acid constants corrected for dissolved solids). What that means for a TA reading of 100 ppm:

Carbonate alkalinity when the test reads TA 100 ppm (our calculation)
CYA	pH 7.2	pH 7.5	pH 7.8
30 ppm	92 ppm	90 ppm	89 ppm
50 ppm	86 ppm	84 ppm	82 ppm
80 ppm	78 ppm	74 ppm	72 ppm
100 ppm	73 ppm	68 ppm	65 ppm

Borates also raise the TA reading slightly. The LSI calculator subtracts them too if you enter a borate level.

So a pool with CYA 80 and a "perfect" TA of 90 actually has about 64 ppm of carbonate alkalinity at pH 7.5. That's fine for chlorine but matters for plaster: it pushes the water toward the corrosive side.

Fix it

Too low: add baking soda (sodium bicarbonate). The calculator on this page gives the amount. For 15,000 gallons, going from 70 to 90 ppm takes about 4.2 lb. Add up to 30 ppm at a time, spread over the surface with the pump running, and retest after a few hours.
Too high: acid plus aeration, in rounds of about 20 ppm. Expect it to take days, not hours.
Keeps drifting: find the cause first (tablets, fill water, heavy acid use) instead of adjusting the number again and again.

All targets, including calcium and stabilizer, are on the pool chemistry chart.

When lowering TA with acid: add acid slowly with the pump running, never mix it with chlorine, and keep pH at 7.2 or above. Wear gloves and eye protection. Always follow the product label.

FAQ

Is 40% alkalinity good for a pool?

Alkalinity is measured in ppm (parts per million), not percent. A TA of 40 ppm is too low: pH will swing with every rain or chlorine dose, and plaster can be etched. Raise it to at least 60–80 ppm. For 15,000 gallons, raising TA from 40 to 80 ppm takes about 8.4 lb of baking soda, added in two or three portions.

What causes pool alkalinity to rise?

Baking soda and soda ash additions, high-alkalinity fill or top-up water concentrating as the pool evaporates, and new plaster. Chlorine itself doesn't raise TA much. If TA keeps climbing without additions, test your tap water.

What causes pool alkalinity to drop?

Acid (muriatic or dry acid), trichlor tablets, non-chlorine shock, and dilution by rain. A pool on tablets typically loses TA steadily through the season, which is why tablet users often need baking soda every few weeks.

Sources

Taylor Technologies, K-1005 instruction manual (TA range, TA before pH): PDF
Taylor Technologies, The Watergram (CYA correction to alkalinity): PDF
PHTA fact sheet, Water conservation during droughts (APSP-11 ranges): phta.org
PHTA fact sheet, Source water and its effects on pool and spa maintenance (2020): phta.org (PDF)