Free Chlorine in Water - DIY Test

The different types of chlorine

For pools and spas, there are 3 types of chlorine you can test, each with its own purpose:

• Total chlorine - testing measures the total amount of chlorine in the water, including free chlorine and combined chlorine. This lets you check whether the total chlorine concentration is within the recommended range for effective disinfection.
• Free chlorine - testing measures the concentration of available chlorine in the water, which is the active chlorine capable of killing bacteria, viruses, and algae. Testing free chlorine regularly is important to ensure adequate water disinfection.
• Combined chlorine - testing measures the amount of chlorine that has bonded with contaminants in the water, forming inactive chlorinated compounds. A high level of combined chlorine may indicate overchlorination or a lack of effective chlorination, which can lead to water quality issues such as skin and eye irritation.

In summary, testing total chlorine helps you monitor overall water disinfection, testing free chlorine ensures effective disinfection, while testing combined chlorine helps you detect potential problems with overchlorination or underchlorination.

A closer look at free chlorine

Sources of free chlorine in water

Free chlorine or Cl2 is chlorine present as hypochlorous acid, hypochlorite ions, or dissolved elemental chlorine. It consists of active and potential chlorine and refers to all chlorine present in the water. It represents the amount of chlorine available to fight bacteria.

Chlorination is a process that involves adding chlorine to water to decontaminate it by killing the microorganisms it contains, acting on most microbes, bacteria, viruses, and germs. However, chlorination does not completely purify water.

Standards for free chlorine in water**

According to the WHO, the free chlorine concentration in treated water should be 0.2 to 0.5 mg/l.

Effects of free chlorine on the body

Significant exposure to free chlorine could damage the respiratory system and lungs. It can also affect the skin, particularly moist areas (armpits, groin, etc.).

Toxic exposure levels :

• 0.2-3.5 ppm : Odor detection threshold
• 1-3 ppm : Mild irritation of mucous membranes, tolerable for up to one hour
• 5 ppm : Moderate eye irritation, tearing, eyelid spasms, burning sensation in the nose and throat, sneezing, coughing - Itchy skin and burning sensation - Intolerable after a few minutes
• 14-21 ppm : Immediate throat irritation
• 30 ppm : Severe upper respiratory tract irritation - Immediate pain behind the breastbone, shortness of breath, coughing, and vomiting 
• 35-50 ppm : Fatal with 60-90 minutes of exposure 
• 40-60 ppm : Pulmonary edema that may lead to death by suffocation, chemical pneumonia and bronchitis, and lung damage 
• 430 ppm : Fatal within 30 minutes 
• 1,000 ppm : Fatal within a few minutes

* This paragraph is based in part on the WHO report “ Guidelines for Drinking-water Quality ”. 

**A guideline value is a reference value provided by the WHO.

Test free chlorine in your water yourself: 2 solutions

Standalone test

This kit contains 50 test strips with tips coated in a reagent that changes color in the presence of free chlorine. This lets you determine the level in your water with the naked eye by visually comparing the strip's color with the color chart printed on the bottle. No additional equipment is required.

This strip test is extremely simple.

Take a test strip and dip it into the water	After about twenty seconds, compare the strip's color with the scale on the back of the container.

The test strip result indicates whether your water contains: 0; 0.25; 0.5; 1; 2; 3; 4; 5; 6; 7; 8; 9; 11; 15; 20; 25 mg/l (or ppm) of free chlorine.

Test free chlorine with a photometer

The second way to test your water at home for free chlorine is with a photometer. On this page, you will find a kit of 100 test strips for use with photometers in the eXact range. This method is very accurate while remaining quick and easy to perform.

This test strip kit is compatible with these photometers : eXat iDip, eXact iDip570, Chlorine+ eXact EZ, Pool eXact EZ, Spa eXact EZ, Chlorine eXact EZ, eXact Eco-Check, eXact Micro 7+, eXact Micro 20 and eXact Micro 10.

Testing with the eXact iDip photometer

These test strips and reagents let you measure free chlorine in your water using the IDIP photometer. Operation is very simple:

1. Open the app on your mobile phone and turn on the photometer.

2. Add water to the tester's designated sample cell

3. Place the test strip (and reagent if needed) in the water for 20 seconds

4. View the result directly on the photometer; the result is automatically saved on your phone.

This water testing system is fast, reliable, modern, expandable, and comprehensive. It is THE most accessible system.

Testing with the Micro 20 photometer

	Take a test strip out of the container before starting the test. Leave it in a dry, easily accessible place, and immediately close the container.
	Turn on the photometer by pressing the ON/ZERO button. The screen will display all indicators, then the selected menu, followed by the most recent results.
	Press the SELECT button repeatedly to choose the group: the free chlorine test belongs to group 1, 3, or 6. Then press the MENU button repeatedly to select the test parameter: CL. (You will find all this information in a table in the user manual supplied with the device.
	Rinse the sample cell at least 3 times with the water you are going to test (to reduce the risk of cross-contamination from your previous test). Finally, completely fill the small cell with the water to be tested.
	Press the ON/ZERO button. The cursor will move across the screen before it displays 0.00PM. This indicates that the sample is ready to be tested.
	Dip the appropriate test strip into the small cell and immediately press the READ button. This will start a 20-second countdown. During the countdown, gently move the strip back and forth (about 1 back-and-forth motion per second). As soon as the "1" disappears from the screen, remove the strip.
	The cursor will move across the screen while the photometer prepares the test results. Record the value displayed for the parameter. This value is automatically saved in the MENU, and if you use the exact iDip app, the results will be saved in its "RESULTS" section. After the test, rinse the cell and clean it with the small brush.

Important: do not discard the sample in the cell if you plan to perform a combined chlorine test afterward.   

Have your water analyzed in a laboratory to test its free chlorine level

You can also have your water analyzed by our partner laboratory. To do so, you first need to purchase a basic analysis, to which you can add a free chlorine test option.