How Much Chlorine to Add to a Pool (by Product and Gallons)
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How much chlorine to add depends on three numbers: how much water you have, how far you want to raise free chlorine, and how strong your product is. The same 1 ppm rise takes about 10 fl oz of 12.5% liquid chlorine but only about 1.5 oz of trichlor in a 10,000-gallon pool.
Raising free chlorine by 1 ppm in 10,000 gallons
| Product | Strength | Amount for +1 ppm |
|---|---|---|
| Liquid chlorine (sodium hypochlorite) | 12.5% | 10.2 fl oz |
| Liquid chlorine (sodium hypochlorite) | 10% | 12.8 fl oz |
| Unscented household bleach | 6% | 21.3 fl oz |
| Cal-hypo (calcium hypochlorite) | 65% | 2.05 oz |
| Cal-hypo (calcium hypochlorite) | 73% | 1.83 oz |
| Trichlor | 90% | 1.48 oz |
| Dichlor | 56% | 2.38 oz |
| Dichlor | 62% | 2.15 oz |
To scale: multiply by the ppm you want to add and by your gallons ÷ 10,000. Example: raising a 15,000-gallon pool by 2 ppm with 10% liquid chlorine takes 12.8 × 2 × 1.5 = 38.4 fl oz.
Why the amounts differ
1 ppm in 10,000 gallons is 37.9 grams of available chlorine (10,000 gallons is 37,854 liters, and 1 ppm is 1 mg per liter). Each product delivers that chlorine at a different strength, so you divide by the strength on the label. Liquid chlorine is labeled in "trade percent", grams per 100 mL, so 12.5% liquid carries 125 grams per liter. The full math is on the chemical calculator page, along with a check against a state health department table.
Household bleach labels give percent by weight, not trade percent, so a bleach dose can be off by a few percent.
How much chlorine you need in the water
The CDC recommends at least 1 ppm free chlorine in pools and at least 3 ppm in hot tubs, with pH between 7.0 and 7.8. If your pool uses cyanuric acid (stabilizer), or a chlorine product that contains it, the CDC says to keep free chlorine at 2 ppm or more. Test chlorine and pH at least twice a day, more often when the pool is busy (CDC).
Trichlor and dichlor both add cyanuric acid each time you use them. See the pool chemistry levels chart for common stabilizer ranges.
Safety
Always read the manufacturer's label: it is the final word on how much to add and how. Only mix chemicals as the label directs, because, in the Virginia Department of Health's words, "improper mixing can cause fire, explosions, or toxic gas." Add chemicals to water, never water to chemicals, and never add them while the pool is in use (Virginia Department of Health).
Sources
- U.S. Centers for Disease Control and Prevention, Home Pool and Hot Tub Water Treatment and Testing.
- Virginia Department of Health, Pool Chemical Safety.
- Dose figures: computed from the formula on the pool chemical calculator page.