Pool alkalinity calculator

Why the formula includes 1.6787

Water tests report total alkalinity as CaCO3 equivalent. Sodium bicarbonate supplies one equivalent per mole, while calcium carbonate represents two. Their equivalent-weight ratio is approximately 1.6787.

Product kg = liters x positive TA increase in ppm x 1.6787 / 1,000,000 / sodium bicarbonate fraction. A 10,000-liter pool needing a 10 ppm TA increase requires about 167.9 grams of pure sodium bicarbonate.

Check that the product is sodium bicarbonate

HASA Alkalinity Up is a documented sodium bicarbonate example. This factor does not apply to sodium carbonate, also called soda ash, or to a blend with unspecified composition. A pH increaser and an alkalinity increaser are not interchangeable by product weight.

After dissolving and circulating as directed, retest both pH and TA. The calculation uses total alkalinity as measured; it does not silently subtract cyanuric acid or convert the reading into carbonate alkalinity for a saturation-index calculation.

If alkalinity is already high

A lower target gives zero bicarbonate addition. Lowering alkalinity involves a different treatment and affects pH; it cannot be modeled by reversing this addition formula. Use a measured acid-demand workflow and qualified pool-care guidance.

Add, circulate, then retest

Follow the product label for application and mixing time, then retest before adding more. Keep chemicals separate: never mix chlorine with acid or other chemicals.