How much liquid chlorine, bleach or shock to add to reach your target, and what target to use for your stabilizer level. The same math the Pool Predictor Pro app uses.
The right chlorine level depends on your stabilizer (CYA). Enter your CYA reading.
Free chlorine is measured in ppm, which is milligrams per liter. One gallon of 12.5% liquid chlorine carries about 473 grams of chlorine, and 10,000 gallons is about 37,854 liters, so one gallon raises 10,000 gallons by about 12.5 ppm. Flip it around and you need about 10 fl oz of 12.5% liquid chlorine per 1 ppm per 10,000 gallons. Everything else scales: twice the pool, twice the chlorine; half the strength, twice the volume.
Dry products work the same way by weight. One pound of 73% cal-hypo raises 10,000 gallons by about 8.75 ppm, and dichlor (56%) needs about 2.4 oz per 1 ppm.
CYA (stabilizer) protects chlorine from sunlight, but it also holds most of it in reserve. The more CYA in the water, the more free chlorine you need for the same sanitizing power. That's why there is no single "right" chlorine number: it's a ratio. This table uses the same rules as the Pool Predictor Pro app.
| CYA | Min FC | Target FC | Salt pool target | SLAM |
|---|---|---|---|---|
| 30 | 2.2 | 3.9 | 3 | 12 |
| 40 | 3 | 5.2 | 3 | 16 |
| 50 | 3.8 | 6.5 | 3.5 | 20 |
| 60 | 4.5 | 7.8 | 4.2 | 24 |
| 70 | 5.2 | 9.1 | 4.9 | 28 |
| 80 | 6 | 10.4 | 5.6 | 32 |
Salt pools can run lower because the cell adds chlorine all day instead of in one daily dose. The SLAM level is for clearing algae; see how to SLAM a pool.
Pool Predictor Pro does this math for you, in the products you own, and forecasts when you will need the next dose, using your pool, equipment and local weather.
Pool Predictor