The baseline — 10.6 fl oz of 12.5% product per 1 ppm per 10,000 gallons — is the standard liquid-chlorine dose used across the pool industry. Weaker products scale up proportionally: the same rise with 6% bleach takes about 22 fl oz.
A worked example
A 15,000-gallon pool testing at 1 ppm FC with a 4 ppm target needs a 3 ppm rise: 10.6 × 1 × 1.5 × 3 ≈ 48 fl oz of 12.5% chlorinating liquid — three-quarters of a half-gallon jug. With 8.25% bleach it's about 72 fl oz, or a bit over half a gallon.
Why your chlorine keeps disappearing
If you dose correctly but FC still crashes daily, the usual suspects are low stabilizer (CYA) letting sunlight strip the chlorine, or algae quietly consuming it. Test CYA first — with none in the water, a sunny afternoon can burn off most of a day's chlorine.
Frequently asked questions
How much liquid chlorine do I add to my pool?
About 10.6 fl oz of 12.5% liquid chlorine raises free chlorine by 1 ppm in 10,000 gallons. Scale by your pool size, your target increase, and your product's strength — regular 6% bleach needs roughly twice the volume of 12.5% pool chlorinating liquid.
What should my pool's free chlorine level be?
3–5 ppm is a common everyday target for a typical residential pool, but the right level depends on your stabilizer (CYA) — higher CYA needs higher FC to sanitize equally. Pools with 30–50 ppm CYA generally run FC around 4–6 ppm.
What's the difference between 6%, 10%, and 12.5% chlorine?
Just concentration. Household bleach is typically 6–8.25% sodium hypochlorite; pool-store 'chlorinating liquid' is 10–12.5%. Stronger product means smaller dose for the same ppm — the calculator adjusts automatically.
When should I add chlorine — day or night?
Evening is best. Sunlight's UV burns off unstabilized chlorine quickly, so a dose added at dusk works overnight instead of evaporating in the afternoon sun.