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:
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:
- Free Chlorine: leftover chlorine that is ready to deactivate bacteria
- 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:
If you have questions about your water quality, the Tap Score Team offers free professional advice 6 days a week.