Not sure? Use the volume calculator.
To raise FC by 3.0 ppm, add
38.5 fl oz (1.2 quarts)
Liquid chlorine 12.5%
How the math works
Raising free chlorine by 1 ppm in 10,000 gallons takes roughly 1.3 oz of pure available chlorine. Products differ in how much available chlorine they carry, which is why the same 1 ppm dose looks so different on the shelf:
| Product | Per 1 ppm per 10,000 gal |
|---|---|
| Liquid chlorine 12.5% | ≈ 10.7 fl oz |
| Liquid chlorine 10% | ≈ 13.4 fl oz |
| Cal-hypo 65% | ≈ 2.1 oz by weight |
| Dichlor 56% | ≈ 2.4 oz by weight |
| Trichlor 90% | ≈ 1.5 oz by weight |
Choosing a target FC
Most service pros run residential pools between 2 and 4 ppm free chlorine, adjusted for season, bather load, and — critically — the pool's CYA (stabilizer) level. The higher the CYA, the more FC you need for the same sanitizing power. If a pool eats chlorine week after week, test CYA before anything else.
Picking dosing side effects matters too: dichlor and trichlor add CYA with every dose, cal-hypo adds calcium, and liquid chlorine adds a little salt. On a weekly route, that's why many pros run liquid as the default and keep tabs for floaters between visits.
Logging doses on the route
A dose only helps next week if it's written down. Tadpole's tech app records readings and exact doses at every stop, so the pool's history is on the customer profile when the “why is it green” call comes. See how it works →
