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It's hard to get trustworthy advice when it comes to your drinking water, so we made Tips for Taps to help answer your questions.
Order a Tap Score Water Test and receive personalized support from professional engineers and scientists by phone, email and chat.

How to Read Chlorine Test Strips

Is there too much chlorine in my water? Too little?

Most water treatment plants utilize chlorination, which involves adding chlorine to drinking water, as part of their disinfection process. When added in the right amounts, chlorine can effectively kill bacteria and prevent against future down-stream contamination. However, to many the thought of drinking chlorine is unsettling and invokes questions such as “What is a safe amount of chlorine in drinking water?” and “Is there too much chlorine in my water?”

Chlorine test strips can quickly tell you how much chlorine is in a sample of water, but sometimes, understanding these seemingly simple results can be tricky. To better understand what test strip results mean, let’s take a look at two types of chlorine testing often included on a chlorine test strip:

  • Total Chlorine and
  • Free Chlorine 
  • Then, we’ll review how to interpret the results of a chlorine test strip and what you might need to do next. 

    Total vs. Free Chlorine 

    During chlorination, chlorine is added to water and reacts with inorganic and organic materials to deactivate bacteria and kill microorganisms. The leftover chlorine that is not used to meet the chlorine demand is called total chlorine

    Total chlorine is made up of: 

    1. Free Chlorine: leftover chlorine that is ready to deactivate bacteria
    2. Combined Chlorine: chlorine that has reacted with inorganic or organic molecules that can no longer deactivate bacteria. Your combined chlorine might include chloramine or trihalomethanes.

    How to Interpret the Results of a Chlorine Test Strip

    Most chlorine test strips measure either free chlorine or both free chlorine and total chlorine in a sample of water. The amount of free chlorine present in drinking water indicates whether or not it is safe to drink. The optimal concentration of chlorine residual is between 0.3 PPM (parts per million) and 0.5 PPM, with levels from 0.2 PPM- 4 PPM considered acceptable. The EPA states that ingesting water with chlorine levels above 4 PPM can cause negative health impacts. 

    Here is a breakdown of the different ranges on a strip test and what each means: 

  • 0 PPM- Not optimal; water with 0 PPM free chlorine will not be disinfected if new bacteria are introduced. 
  • 0.5 PPM- Optimal; a free chlorine level of 0.5 PPM ensures water will remain bacteria free, even if new bacteria are introduced. 
  • 1 PPM- Good; Ensures water will remain bacteria free, even if new bacteria are introduced.
  • 2 PPM- Not optimal; once there is 2 PPM free chlorine present in water, it starts to have an unpleasant taste and odor. 
  • >2 PPM- Bad; while chlorine in water isn’t considered dangerous until it reaches above 4 PPM, water with 2 PPM chlorine tastes and smells like chemicals. Further testing would be required to determine if chlorine content is above the 4 PPM threshold. 
  • If you have questions about your water quality, the Tap Score Team offers free professional advice 6 days a week.

    It's hard to get trustworthy advice when it comes to your drinking water, so we made Tips for Taps to help answer your questions. Order a Tap Score Water Test and receive personalized support from professional engineers and scientists by phone, email and chat.

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