An estimate. Baking soda raises alkalinity with little effect on pH; acid lowers both, so add it in stages and retest between additions.
You need
6.8lbs baking soda
To raise total alkalinity 30 ppm in 15,000 gallons. Aim for 80-120 ppm.
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To raise total alkalinity, add about 1.5 pounds of baking soda per 10,000 gallons for every 10 ppm you need. To lower it, add acid in stages and retest, because acid lowers pH at the same time. Enter your gallons and current and target alkalinity to get the dose.
How it works
Using the pool alkalinity calculator
What total alkalinity should be
Aim for 80 to 120 ppm total alkalinity. Alkalinity is the buffer that keeps pH stable, so when it drifts, pH starts bouncing and nothing else holds. Get alkalinity into range first, then adjust pH, because correcting them in the wrong order means redoing the work.
Raising alkalinity with baking soda
Sodium bicarbonate (baking soda) raises total alkalinity with little effect on pH. About 1.5 pounds per 10,000 gallons lifts alkalinity roughly 10 ppm. Broadcast it across the pool with the pump running, let it circulate for a few hours, then retest before adding more.
Lowering alkalinity takes stages
Acid lowers both total alkalinity and pH together, so there is no single clean dose. Add muriatic or dry acid in stages, circulate, and retest between additions rather than dumping a full correction at once. Doing it gradually is how you avoid driving pH too low and having to bring it back up.
FAQ
Common questions
How much baking soda do I add to raise pool alkalinity?
About 1.5 pounds of baking soda per 10,000 gallons raises total alkalinity by roughly 10 ppm. So a 15,000-gallon pool that needs to come up 20 ppm takes about 4.5 pounds. Add it with the pump running, let it circulate, and retest before adding more.
What should pool alkalinity be?
Total alkalinity should be 80 to 120 ppm. Alkalinity buffers pH and keeps it from swinging, so set it into range before you adjust pH. Below 80 ppm pH becomes unstable; above 120 ppm pH tends to drift up and scale can form.
How do I lower alkalinity in a pool?
Add acid - muriatic acid or dry acid (sodium bisulfate) - in stages, circulating and retesting between additions. There is no exact single dose because acid lowers pH along with alkalinity. Work down gradually toward your target rather than making one large correction.
Does lowering alkalinity also lower pH?
Yes. Acid lowers total alkalinity and pH at the same time, which is why you cannot adjust one without moving the other. Lower alkalinity in stages, then bring pH back up if it dropped too far, often by aerating the water. Expect to balance the two together rather than separately.
