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How to lower chlorine in a pool
First, stop adding chlorine and turn down any feeder or salt cell. Most high readings then fall by themselves within a day or two.
Four ways, easiest first
- Sun: take off the cover and let UV break chlorine down. This is fastest with little stabilizer in the water.
- Time and use: keep the pump on and wait. Chlorine falls as it reacts with what is in the water.
- Fresh water: replacing 20% of the water lowers chlorine by about 20%.
- Neutralizer: sodium thiosulfate lowers chlorine quickly. Follow the label closely, since it is easy to overdo. It can also leave your pool struggling to hold chlorine later.
When can you swim?
The CDC's model code for public pools sets a ceiling of 10 ppm for free chlorine when bathers are in the water, and 8 ppm for bromine. Many owners wait until it is under 5 ppm for comfort.
DPD test kits can bleach out and read low or even zero above 10 ppm, as the CDC warns. If a high-chlorine pool suddenly reads zero, dilute the sample with tap water and test again.