Water Purification Experiment: Removing Chlorine From Water

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Author: Beth Touchette

Chlorine is a chemical added to water supplies to kill microorganisms. Microorganisms are tiny living things like bacteria, viruses, and protozoans that cannot be seen with the naked eye. Cholera, typhoid fever, and dysentery are all caused by microorganisms in water. Before chlorine was routinely added to water supplies, thousands of people died because of water-borne diseases. A disinfectant is a substance that kills microorganisms. One well known disinfectant is soap. Chloramine is another disinfectant that is often added to water supplies instead of chlorine.

Unfortunately, small animals, especially fish, are sensitive to chlorine and chloramine. Chlorine and chloramine can also react with compounds in the water, forming potentially hazardous new substances. This is why it is absolutely necessary to remove chlorine and chloramine from your tap water before setting up a fish tank. 

Problem: What's the best way to remove chlorine and chloramine in water?  


  • Chlorine and chloramine test strips (combo strips that test for both and a couple other substances are available at pet stores)
  • Tap water
  • Swimming pool water
  • Distilled water (available at grocery stores)
  • Clean non-metal containers for holding water samples
  • Stove
  • 3 very clean pots
  • Chemical dechlorinator (also available at pet stores, often called “water conditioner”)
  • Carbon over-the-tap or carafe-type water filter


  1. Follow the instructions for your chlorine/chloramine test strips to record the amount of chlorine/chloramine in each of your water samples.  Make sure all your samples are the same temperature.  Make a data table like this one:


 Initial Amount of Chlorine

Initial Amount of Chloramine 

Tap water



Distilled water



Pool water




  1. Now that you have some idea of how much disinfectant are in different sources of water, you can try different ways of removing the disinfectants from the tap water.
  2. Pour a sample of tap water into an open container and let it sit for 24 hours.
  3. Test the water for disinfectants, record in a second data table.

Tap Water Treatment

Final Chlorine Amount

Final Chloramine Amount







Chemical Removal



Carbon filter




  1. Boil a pot of tap water for fifteen minutes. Let cool.
  2. Test the boiled water for disinfectants, record data.
  3. Treat a third sample of tap water with the chemical dechlorinator.
  4. Test treated water sample for chlorine and chloramine, record data.
  5. Use the carbon filter to treat a fourth sample of tap water.
  6. Test the carbon treated sample for chlorine and chloramine, record data.
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