Calculators / Pool
Pool chlorine calculator: how much chlorine to add?
Test your free chlorine and pick what you add. You'll get the fluid ounces or pounds to get back to 2 to 4 ppm.
Updated · How we check our numbers
Add this much
38 fl oz of liquid chlorine
That's 0.3 gal of 12.5% liquid chlorine to take 18,193 gallons from 1 to 3 ppm.
- Pool
- 18,193 gal
- Now
- 1 ppm
- Target
- 3 ppm
- Liquid
- 38 fl oz0.3 gal
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Estimate for planning only, not professional advice. Check the manufacturer’s instructions, your local code and a licensed professional before you buy, build or install. Use at your own risk. Terms.
surface = 32 ft × 16 ft = 512 sq ft
average depth = (3.5 + 6) ÷ 2 = 4.75 ft
gallons = 512 sq ft × 4.75 ft × 7.48 = 18,193 gal
raise = 3 − 1 = 2 ppm
liquid chlorine = 18,193 gal × 2 ppm ÷ (10,000 × 12.5) = 0.29 gal
Pour it in front of a return jet with the pump on, and retest after the water has run through the filter for a few hours.
Test free chlorine, not total. A cheap test strip reads both, and the gap between them is used-up chlorine.
How we work it out
Liquid chlorine is the easy one. A gallon of 12.5% raises 10,000 gallons of water by 12.5 ppm. A gallon of 10% raises it 10 ppm.
liquid (gal) = pool gallons × ppm to raise ÷ (10,000 × strength)
granular (lb) = pool gallons × ppm to raise × 8.34 ÷ 1,000,000 ÷ percent available chlorine
The percent on a granular label is available chlorine, so 65% cal hypo is 0.65 in the math. The CDC wants at least 1 ppm in a home pool. Hayward and Pentair say 1 to 3, and Pentair points to 2 to 4 from the pool industry group. Past 10 ppm, you're shocking, not topping up.
Where the numbers come from
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