I am looking to install a water filter system and I wanted to test the water for free and total chlorine.

I understand from the city water report that it uses chloramine and NO chlorine (test report)and that chloramine content averages around 4 ppm in the water supply. I purchased one of these to test it out. http://www.bulkreefsupply.com/insta-test-free-total-chlorine-strips-lamotte.html

The above product can measure free and total chlorine ( 0, 0.5, 1, 3, 5, 10 ) PPMs. I was surprised to find out after using these test strips that city supply has 0 PPM for both free and total chlorine.

Questions 1. Any idea how I can test if these test strips are indeed working? 2. Anything wrong with the way I have tested?

  • 4
    $\begingroup$ As water goes through pipes it loses active chlorine due to reaction with biological material, dissolved substances and even the pipe, so it is possible there is little left by the time it reaches your house. Your local water department should provide testing for your water so you can verify this, or you could make up a known concentration of bleach in distilled water, using serial dilution to 0.5 ppm, to check that the strips are accurate. $\endgroup$ Mar 6, 2015 at 18:18
  • 2
    $\begingroup$ Tried the method that you suggested, the test strips work. $\endgroup$
    – Harkish
    Mar 18, 2015 at 19:39

1 Answer 1


Test strips for chlorine should work for both chlorine- and chloramine-treated water. See Here-to-learn's comments to this answer for the chemical kinetic reason why chlorine test strips will also work for chloramine-treated water.

Notice that your city supplies the water with chloramine. Depending on how much chloramine is present in your tap water, leaving water to sit for days on the countertop would be necessary to remove a significant amount of chloramine.

Please see this research paper: http://hbd.org/ajdelange/Brewing_articles/BT_Chlorine.pdf

Page 17 estimates the half-lives of chlorine vs. chloramine.

Half Life of Chlorine & Chloramine Chart

  • 1
    $\begingroup$ This is incorrect advice and should be removed. Dr. Pippik was correct in hypothesizing that the chloramines are likely reacting with biological material (biofilms) in the distribution system, thus it is below the strip detection limit when it arrives at the tap. The test strips are for detecting free chlorine and total chlorine. Total chlorine is the sum of free chlorine (i.e., hypochlorous acid and hypochlorite) and combined chlorine (i.e., mono-, di-, and tri- chloramine), thus the strips do measure the presence of chloramine. $\endgroup$ May 9, 2017 at 12:52
  • $\begingroup$ @Here-to-learn, thanks for the comment. I agree that my answer should be revised, but my answer also points to a good source proving that chloramine has a much longer half-life. It would be excessive to delete the entire answer. Also, I'm pretty sure chloramine is less reactive to biological material than chlorine. Are you aware of this fact? $\endgroup$
    – N4v
    May 9, 2017 at 21:27
  • $\begingroup$ Yes, as a disinfectant, chloramine is well known to have slower kinetics compared to other disinfectants (e.g., its CT is two orders of magnitude worse than chlorine for viruses). But, your answer is not really an answer to the original question, as it neither answered (1) or (2). Rather, you should have put it as a comment for discussion. I would also argue that a broken link to a brewing site is not a good source. And finally, you suggested the OP use "test strips that are made for testing chloramin," which they did, so that's not really a relevant answer. $\endgroup$ May 10, 2017 at 23:50
  • $\begingroup$ I think what you might have been suggesting is that chloramine will react much slower than free chlorine and thus it should still be present at the tap - is that correct? That would only be the case if the utility was using the same molar concentrations; however, chloramine, because of its slower kinetics, is typically dosed at smaller concentrations knowing it will stay in the distribution system longer. Even if we assume that high concentrations were used, we don't know the distance to OP's house, thus we can't make kinetic conclusions. And, we don't know strip detection limit. $\endgroup$ May 10, 2017 at 23:56
  • 1
    $\begingroup$ I took a screenshot and uploaded/edited as an image. $\endgroup$ Oct 4, 2017 at 20:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.