Water Chemistry

pH and Alkalinity Basics for Pool Owners

Most "I can't get my pH right" problems are actually alkalinity problems wearing a different number. This site is dedicated to a single build method: gunite (shotcrete) construction, rebar cage, sprayed and hand-finished concrete, engineered bond beams, and a design that can be shaped to anything the lot allows, from tanning ledges to negative edges to integrated spas.

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Alkalinity Is the Buffer, pH Is the Target

Total alkalinity (measured in ppm) resists sudden pH swings. Too low, and pH bounces with every rain event, swimmer load, or chemical addition; too high, and pH gets locked in place and resists correction even with repeated dosing.

The practical range to aim for is 80-120 ppm alkalinity and 7.2-7.6 pH. Fix alkalinity first if it is out of range, then adjust pH; doing it in the other order usually means re-doing the pH correction once alkalinity shifts it again.

What Throws These Numbers Off

Heavy rain (common in the Houston area) dilutes alkalinity and can drop pH; pool plaster naturally leaches calcium and can raise pH slightly over time; and chlorine products themselves are mildly acidic or basic depending on the type used, which nudges both numbers with routine dosing.

Muriatic acid or sodium bisulfate lower both pH and (more slowly) alkalinity; sodium bicarbonate raises alkalinity with a smaller pH effect; soda ash raises pH directly. Knowing which lever moves which number is most of what "balancing" a pool actually is.