Let the sun lower it (the easy way)
Chlorine breaks down in sunlight, so the simplest fix is to stop adding any, remove any chlorine tablets or floaters, and let the pool sit uncovered in the sun with the pump running. Free chlorine often drops noticeably within a day, faster if your cyanuric acid is low and the sun is strong.
For a mild overshoot, this is all you need. Just hold off on swimming until it comes down to a comfortable level and retest with the chlorine calculator workflow in mind.
Neutralize it for a fast drop
When you need chlorine down quickly, use a chlorine neutralizer, sodium thiosulfate, sold as chlorine reducer. It lowers chlorine fast, but it is easy to overshoot and drive chlorine to zero, so add small amounts, circulate, and retest before adding more. Follow the product label for the dose.
Non-chlorine shock products do not lower chlorine, so reach for an actual neutralizer if that is the goal. After neutralizing, recheck pH, since these products can nudge it.
Dilute it
Draining some water and refilling with fresh water dilutes chlorine along with everything else. It is slower and wastes water, so it is rarely the first choice just for chlorine, but if you were already going to replace water for another reason, it brings chlorine down as a bonus.
When is it safe to swim?
High chlorine is uncomfortable and can irritate eyes and skin and fade swimwear, but it is mainly a wait-it-out situation. A common guideline is to swim once free chlorine is back within normal range, roughly at or below the shock level for your cyanuric acid and ideally near your normal target. If you shocked the pool, that is the same patience: wait for it to fall back to range, then enjoy it.
Frequently asked questions
How do I lower chlorine in my pool?
Three ways: stop adding chlorine and let sunlight burn it off with the pump running, which handles most cases in a day or so; use a chlorine neutralizer (sodium thiosulfate) for a fast drop, adding small amounts and retesting; or dilute by draining and refilling some water. For a mild overshoot, the sun is the easiest fix.
What neutralizes chlorine in a pool?
Sodium thiosulfate, sold as chlorine neutralizer or chlorine reducer. It lowers free chlorine quickly, but it is easy to overshoot to zero, so add it in small amounts, circulate, and retest before adding more. Recheck pH afterward, since it can shift it slightly.
How long does it take for pool chlorine to drop?
With the sun and no new chlorine added, free chlorine often falls noticeably within a day, faster when cyanuric acid is low and the sun is strong, slower when CYA is high. A neutralizer lowers it in minutes. Diluting by replacing water is the slowest option.
Is it safe to swim with high chlorine?
High chlorine is uncomfortable and can irritate eyes and skin and fade swimwear, so it is best to wait. A common guideline is to swim once free chlorine has fallen back within your normal range. If you shocked the pool, wait for it to drop to that range before getting in.
Will baking soda lower chlorine?
No. Baking soda raises total alkalinity and does not lower chlorine. To reduce chlorine, let sunlight break it down, use a sodium thiosulfate neutralizer, or dilute with fresh water. Do not confuse non-chlorine shock with a neutralizer either; it does not lower chlorine.