How Much Shock or Chlorine to Add to a Pool: Ounces by Size
The dose is simple arithmetic: ppm to add × gallons × 8.34 ÷ 1,000,000 pounds of pure chlorine, divided by the strength of the product. For a 15,000 gallon pool, raising free chlorine by 10 ppm takes 31 oz of 65% calcium hypochlorite. The pool chemical dose calculator does it for any size, product and target.
Part of the project planners: Planning pools, ponds and water storage and Summer projects for the house and the yard.
Ounces to raise a pool by 10 ppm
From 0 to 10 ppm, by pool size and product:
| Pool size | Cal hypo 65% (oz) | Trichlor 90% (oz) | Liquid 12.5% (fl oz) |
|---|---|---|---|
| 8,000 gal | 16 oz | 12 oz | 82 fl oz |
| 10,000 gal | 21 oz | 15 oz | 102 fl oz |
| 15,000 gal | 31 oz | 22 oz | 154 fl oz |
| 20,000 gal | 41 oz | 30 oz | 205 fl oz |
| 25,000 gal | 51 oz | 37 oz | 256 fl oz |
| 30,000 gal | 62 oz | 44 oz | 307 fl oz |
Per 1 ppm in 10,000 gallons
| Product | Per 1 ppm |
|---|---|
| Calcium hypochlorite (65%) | 2.1 oz |
| Dichlor (56%) | 2.4 oz |
| Trichlor (90%) | 1.5 oz |
| Liquid chlorine (12.5%) | 10.2 fl oz |
| Liquid chlorine (10%) | 12.8 fl oz |
These match the county health-department dose charts, which round them to 2 oz of cal hypo, 2.5 oz of dichlor, 1.5 oz of trichlor and 10 to 13 fl oz of liquid. The strength is the available chlorine on your label, so a 73% shock needs less than a 65% one.
What each product leaves behind
- Calcium hypochlorite adds calcium hardness, about 7 ppm for a 10 ppm dose.
- Dichlor and trichlor add cyanuric acid (stabilizer): about 9 ppm and 6 ppm for a 10 ppm dose. Too much stabilizer makes chlorine less effective.
- Liquid chlorine adds neither, but it loses strength in heat and with age.
Target levels
CDC's home pool guidance is at least 1 ppm free chlorine in a pool, or 2 ppm when the pool uses cyanuric acid, dichlor or trichlor, with pH 7.0 to 7.8. Shock levels and the wait before swimming are set by the product label. Above about 10 ppm many test kits bleach out and read falsely low.
Alkalinity
Total alkalinity is raised with baking soda, about 1.4 lb per 10 ppm in 10,000 gallons, and lowered with muriatic acid (31.45%), about 25.6 fl oz per 10 ppm in 10,000 gallons. For a 15,000 gallon pool, 60 to 100 ppm takes 8.4 lb of baking soda. Add in portions and retest. Use the alkalinity range from your pool or liner maker.
Safety
- Never mix chlorine products with each other or with acid.
- Add chemicals to the water, never water to the chemical.
- Wear goggles and gloves, and store chemicals dry, closed and apart.
- Keep swimmers out until your test shows a safe level.
Find the gallons first with the pool volume calculator, and size salt with the pool salt calculator.
Frequently asked questions
How much shock do I add to a 15,000 gallon pool?
To raise free chlorine by 10 ppm with 65% calcium hypochlorite, 31 oz (1.9 lb). The label of the shock you buy gives its own dose, so use that if it differs.
How many ounces of liquid chlorine raise a pool 1 ppm?
About 10 fl oz of 12.5% liquid chlorine in 10,000 gallons, or 13 fl oz of 10%.
How much does shock raise cyanuric acid?
Calcium hypochlorite adds none. Dichlor does: a 10 ppm dose leaves about 9 ppm of cyanuric acid, and trichlor about 6 ppm.
What free chlorine level should a pool have?
CDC advises at least 1 ppm in a pool, or 2 ppm if the pool uses cyanuric acid, dichlor or trichlor, with pH between 7.0 and 7.8.
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