Shock to 10x combined chlorine, at night.

Shock to 10x your combined chlorine level, or just raise free chlorine to 10 ppm if you don’t know your combined chlorine.

Breakpoint chlorination is math, not magic. Test your water first. Find the combined chlorine (total chlorine minus free chlorine). Multiply that number by 10. That’s how much shock you need.

But most people don’t test combined chlorine. That’s fine. Just dump in enough granular shock or liquid chlorine to get to 10 ppm free chlorine. For a typical 20,000 gallon pool, that’s about 2 gallons of 10% liquid chlorine or one pound of calcium hypochlorite shock per 10,000 gallons.

Do it at night. Sunlight burns off chlorine fast. Run the pump overnight. Test the next morning. If it smells like chlorine again (the real smell of clean water, not the locker room smell), you’re good. If it still stinks, you missed the breakpoint and need to do it again.

You’ll know you hit it when the water turns from dull to sparkling. The chloramines are gone.