How Much Chlorine

How to Raise Alkalinity in a Pool (Baking Soda Amounts by Gallons)

By Tam Vu · Updated

On this page
  1. What level to aim for
  2. The formula
  3. Pounds of baking soda for +10 ppm
  4. Adding it safely
  5. Safety and the label
  6. Sources

Total alkalinity is a test reading in ppm. When it reads low, plain baking soda (sodium bicarbonate) raises it. The amount depends on your pool's volume and on how far you need to go, and the arithmetic is the same every time.

Raise total alkalinity

The 60 and 90 ppm values are example numbers only. Use your own test reading. If the target is lower than your reading, the calculator shows the acid amount to lower it instead.

What level to aim for

A public pool code, Columbus Public Health's water chemistry sheet, lists total alkalinity of at least 60 ppm, ideally 80 to 120 ppm (Columbus Public Health). That is a standard for public pools, so treat it as a reference for a home pool, and follow your pool maker's guidance if it differs. The CDC does not give an alkalinity range. See the full levels chart for the sources side by side.

The formula

Alkalinity is reported as if it were calcium carbonate, and baking soda (NaHCO₃, 84.007 g per mole) supplies alkalinity at a rate of one mole per mole. Calcium carbonate counts as 50.04 g per equivalent. With 1 ppm equal to 1 mg per liter:

grams of baking soda = gallons × 3.785 × ppm to add × 84.007 ÷ 50.04 ÷ 1,000

That is about 1.40 lb per 10 ppm in 10,000 gallons, or 1.68 mg of baking soda for each 1 mg/L of alkalinity you add.

Example: a 15,000-gallon pool reads 60 ppm and you want 90. Add 30 ppm: 15,000 × 3.785 × 30 × 84.007 ÷ 50.04 ÷ 1,000 = 2,860 g, which is 6.3 lb of baking soda.

Pounds of baking soda for +10 ppm

Pool size Baking soda for +10 ppm
5,000 gallons 0.70 lb
10,000 gallons 1.40 lb
15,000 gallons 2.10 lb
20,000 gallons 2.80 lb
30,000 gallons 4.20 lb

For a bigger rise, scale in proportion: +30 ppm takes three times these amounts. The Indiana Department of Health's chemical adjustment sheet lists the same 1.4 lb per 10 ppm for 10,000 gallons (Indiana DOH).

Adding it safely

  • Know your gallons. Use the pool volume calculator if you are not sure.
  • Add in parts and retest. Mixing is not instant. Add part of the amount, run the pump, wait, and test again before adding more.
  • Test with a fresh sample. An old or poor test strip can be off by enough to matter. The CDC says DPD test kits are the most accurate, and strips less so (CDC).
  • If the reading ends up too high, see the acid amount in the calculator above (enter a target below your reading).

Safety and the label

The calculator works from the strength you select; the label on your product is the final word. Virginia's Department of Health says to mix chemicals only as the label directs, add chemicals to water and never water to chemicals, store liquids below dry products in their original containers, and wear the protective gear the label lists (VDH).

Sources