How much chlorine to add to a pool The short answer How much chlorine to add depends on your pool size, how far chlorine is below where it should be, and your stabilizer (CYA), which sets that level. As a guide, about 13 fl oz of 10% liquid chlorine raises 10,000 gallons by 1 ppm. Type your numbers below for the exact amount in the product you have.
How much chlorine your pool needs Free chlorine now
The chlorine that is working right now — it kills germs and algae.
Free chlorine you want
Good range: 2.3–12 ppm.
Type the size and your chlorine reading.
Step by step Test free chlorine and stabilizer (CYA).
Aim for about 11.5% of your stabilizer level, and never below 7.5% of it — with CYA 40 that is about 5 ppm.
Work out the amount with the calculator on this page, for the chlorine you have.
Add it in the evening, in front of a return jet, with the pump running.
The product label always wins — if it says something different, follow the label.
Why it happens Sunlight, swimmers, rain and warm water all use chlorine up, so a pool needs some every day or two.
Stabilizer protects chlorine from the sun — but the more of it there is, the more chlorine you need.
Questions Liquid chlorine or bleach? The same chemical: liquid pool chlorine is just stronger (10–12.5% against 6–8.25%). Use only plain, unscented bleach.
What should my chlorine level be? At least 7.5% of your stabilizer level, aiming for about 11.5%: with CYA 40 that is 3 ppm at the least and about 5 ppm to aim for.
How often should I add chlorine? In summer most pools need some every day or two. Test and top up to the level your stabilizer calls for.
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