How to Minimize Chlorine in a Swimming Pool

A chlorine feeder can bump up chlorine levels too high.

If the chlorine level reads above 5.5 parts per million (ppm), you can do a few things to lower it before adding a chemical to the water. Turn down the automatic chlorine feeder if you are using one or stop adding liquid or granular chlorine to the pool until the chlorine level minimizes. If you don't have time to wait a few days to minimize the chlorine level, you can use sodium thiosulfate to lower the chlorine.

Things You'll Need

• Test strip kit
• Sodium thiosulfate (chlorine neutralizer)
• Bucket

Instructions

1. Backwash the pool filter until the water runs clean through the sight glass. If the filter is a diatomaceous earth (DE) filter, add DE powder to the filter as you would after backwashing.

2. Turn on the pool filter. Dip one chlorine test strip in the water at the deep end of the pool. Compare the strip to the chart in the kit. This will tell you how high the chlorine level is and how much to lower it.

3. Measure the amount of sodium thiosulfate needed and pour into a bucket. If the chlorine level is over 5 ppm, add 6 oz. of sodium thiosulfate per 10,000 gallons of water. If the chlorine is over 10 ppm, add 12 oz. of sodium thiosulfate per 10,000 gallons. If the chlorine reading is above 20 ppm, add 28 oz. per 10,000 gallons.

4. Remove the cover from the skimmer. Pour the bucket of sodium thiosulfate into the skimmer. Replace the cover on the skimmer. Continue to run the pool pump for at least eight hours. Do not backwash the pool for at least 24 hours after adding the chlorine neutralizer.

5. Retest the pool water the next day. Assuming the chlorine level is within range, which is 1.0 to 3.0 ppm, you can resume normal filtration and backwash the pool as needed.

Tips & Warnings

• Wear gloves and goggles when measuring and adding chemicals to pool water.

References

• Pool Manual: Chlorine