Guides / Pool chlorine calculator: how much to add
Pool chlorine calculator: how much to add
Two small tools. First, what free chlorine your water needs (it depends on how much stabilizer, CYA, is in it). Second, how much of your chlorine product raises it to that level.
1. What free chlorine should I have?
Rule used: minimum = 7.5 percent of CYA (4.5 percent with a salt generator), at least 1 ppm in a pool and 3 ppm in a hot tub. Target = minimum + 2 ppm. Shock = 40 percent of CYA (10 ppm if CYA is under 25). The same relationship Clearly uses.
2. How much chlorine do I add?
Based on the common relationship: about 12.8 fl oz of 10 percent liquid chlorine raises free chlorine by 1 ppm in 10,000 US gallons. Dry calcium hypochlorite also adds calcium. Dose in steps, retest and adjust; real water loses chlorine to sunlight and organic matter.
Using the result
- Test free chlorine and CYA with a reliable kit (a drop-based FAS-DPD or a good photometer beats strips for CYA).
- Use the first tool for your target, the second for the amount. Add about half to start if you are unsure of your volume.
- Add liquid chlorine with the pump running, poured slowly near a return jet, in the evening so the sun does not burn it off.
- Retest after a few hours of circulation and adjust.
Related: Pool volume calculator and how to fix green pool water.
Want a step-by-step plan from your own test?
Clearly turns your pool or hot tub water test into an ordered plan: what to add, how much and in what order, for any brand of chemicals. It works offline and needs no account.
Clearly by Pulad Labs (Istanbul). Android, available on Google Play.
General information, not professional advice. Always follow the product label and your pool manufacturer's guidance. Never mix chemicals, add chemical to water (not water to chemical), wear eye and skin protection, and keep children and pets away while treating the water.
Frequently asked questions
How much chlorine do I add to my pool?
About 12.8 fl oz of 10 percent liquid chlorine raises free chlorine by 1 ppm in 10,000 US gallons. Use the calculator for your volume, your product strength and the ppm you need.
What free chlorine level should I have?
It depends on stabilizer (CYA). A common rule is at least 7.5 percent of CYA, so 3 ppm at 40 ppm CYA, and never below 1 ppm in a pool or 3 ppm in a hot tub.
What is the shock level?
Roughly 40 percent of your CYA, or 10 ppm if CYA is under 25. It is used to clear algae or high combined chlorine.