An estimate from each product's typical available-chlorine strength. Add with the pump running, shock at dusk, and always retest before anyone swims.
You need
32fl oz
Of liquid chlorine (12.5%) to raise free chlorine 2 ppm in 15,000 gallons.
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The chlorine dose depends on the product. Liquid chlorine, cal hypo, and dichlor each add a different amount of available chlorine per ounce. Enter your gallons, current and target free chlorine, and product to get the amount to add. To shock, raise free chlorine to about 10 times your combined chlorine reading.
How it works
Using the pool chlorine calculator
Products are not interchangeable by weight
Liquid chlorine is about 12.5 percent available chlorine, cal hypo is about 73 percent, and dichlor is about 56 percent and stabilized. Because the strengths differ, the same target needs very different amounts of each. The calculator uses the right constant per product so you are not converting in your head on the pool deck.
Routine dose versus a shock
A routine dose nudges free chlorine back into the 1 to 3 ppm range. A shock drives it much higher to clear combined chlorine (chloramines), the cause of that strong chlorine smell. The common rule is to raise free chlorine to about 10 times the combined chlorine reading, known as breakpoint chlorination.
Add, circulate, and retest
Add chlorine with the pump running and, for a shock, do it at dusk so sunlight does not burn it off before it works. Retest before anyone swims. Logging the dose and the resulting reading on the pool record is how you spot a pool that keeps demanding chlorine, which usually points to a deeper problem.
FAQ
Common questions
How much chlorine do I add to my pool?
It depends on the product and how far you need to raise free chlorine. Liquid chlorine at 12.5 percent takes about 10.7 fluid ounces to raise 10,000 gallons by 1 ppm; cal hypo takes about 2 ounces by weight; dichlor about 2.7 ounces. Enter your gallons and target above to get the exact amount.
How much liquid chlorine do I need to shock a pool?
To shock, raise free chlorine to about 10 times the combined chlorine reading. At 12.5 percent, roughly one gallon of liquid chlorine raises 10,000 gallons by about 12 ppm, so a typical shock in a 15,000-gallon pool is one to two gallons. Add at dusk with the pump running and retest before swimming.
What is breakpoint chlorination?
Breakpoint chlorination is adding enough chlorine to fully burn off combined chlorine (chloramines) rather than leaving partial compounds that still smell and irritate. The practical rule is to raise free chlorine to about 10 times the combined chlorine level in one dose. Stopping short can make the smell and irritation worse.
How long after shocking a pool can you swim?
Wait until free chlorine falls back to about 1 to 3 ppm, which is usually 24 hours after a normal shock but can be longer after a heavy one. Always retest before swimming rather than guessing by time. Swimming in heavily over-chlorinated water can irritate skin and eyes.
