⚠️ Corrosive. Eye protection and gloves; add acid to water, never the reverse; never mix with chlorine. Dose in stages, retest between additions, and keep swimmers out until pH is back in range (7.2–7.8).
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The acid dosing formula
fl oz = 25.6 × (31.45 ÷ strength %) × (gallons ÷ 10,000) × (TA drop ÷ 10)
The ~26 fl oz per 10 ppm per 10,000 gallons figure for full-strength acid is the standard industry dose. Because acid drops pH along with TA, big corrections should always be split: dose a third to a half, let it circulate an hour, test pH, and continue only if pH is still above ~7.2.
A worked example
A 15,000-gallon pool at 140 ppm TA targeting 90: a 50 ppm drop needs 25.6 × 1 × 1.5 × 5 ≈ 192 fl oz — 1.5 gallons of full-strength acid, added over two or three sessions across a couple of days, never all at once. Between doses, run water features to aerate: that lifts pH back up while leaving the new, lower TA in place.
The lower-TA-without-crashing-pH method
The cycle is: acid drops both TA and pH → aeration raises pH only → repeat until TA hits target with pH in range. It feels slow and it is — but it's the only way down. A pool with a salt cell aerates itself, which is why SWG pools drift this direction naturally and need acid more often.
Frequently asked questions
How much muriatic acid do I add to lower alkalinity?
Roughly 26 fl oz of full-strength (31.45%) muriatic acid lowers total alkalinity by 10 ppm in 10,000 gallons. Half-strength (14.5%) products need about twice the volume.
Does muriatic acid lower pH or alkalinity?
Both, always — acid can't target one. The practical trick: dosing acid lowers TA and pH together, then aerating the water (fountains, jets pointed up) raises pH back without raising TA. That combination is how you lower TA alone.
How do I add muriatic acid safely?
Wear eye protection and gloves; add acid to water, never water to acid; pour slowly into the deep end with the pump running, away from walls and fittings; never mix with chlorine or any other chemical — the fumes are dangerous. Store it outdoors or in a ventilated space away from metals.
Why does my pool's pH keep climbing?
Usually high TA (the water outgasses CO2 and drifts pH up), a salt water generator (aeration at the cell), or fresh plaster. If you're adding acid weekly, check TA — lowering it into the 70–90 range slows the climb.