Why Is There Chlorine in Tap Water?

To kill germs. The CDC says water utilities add a disinfectant to tap water to kill germs and prevent people from getting sick, usually chlorine or chloramine. The EPA says chloramines, most commonly formed by adding ammonia to chlorine, provide longer-lasting disinfection as water travels through the pipes.

The CDC says chlorine or chloramine levels up to 4 milligrams per liter are considered safe in drinking water and unlikely to make people sick. The EPA sets a maximum residual disinfectant level, the highest level of a disinfectant allowed, and says there is convincing evidence that adding a disinfectant is necessary to control microbial contaminants.

Disinfection has a trade-off. A 2001 EPA fact sheet says disinfectants react with matter in the water to form disinfection byproducts, several of which, such as chloroform and bromate, have been shown to be carcinogenic in laboratory animals, and that some studies have suggested a weak association between certain cancers, such as bladder cancer, and exposure to chlorinated surface water. The EPA and CDC say the benefits of disinfection outweigh the potential risks from those byproducts.

Sources checked September 15, 2026. Every point below links the page it came from.

The sources behind this answer

  • Government sourceThe CDC says utilities add a disinfectant to tap water to kill germs and prevent illness, usually chlorine or chloramine and less commonly chlorine dioxide. US CDC ↗
  • Government sourceThe EPA says chloramines are most commonly formed by adding ammonia to chlorine, and provide longer-lasting disinfection as water moves through pipes. US EPA ↗
  • Regulatory filingThe EPA defines the maximum residual disinfectant level as the highest level of a disinfectant allowed in drinking water, and says adding a disinfectant is necessary to control microbial contaminants. US EPA ↗
  • Government sourceThe CDC says chlorine or chloramine levels up to 4 milligrams per liter are considered safe in drinking water and unlikely to make people sick. US CDC ↗
  • Government sourceA 2001 EPA fact sheet says disinfection byproducts such as chloroform and bromate have been shown to be carcinogenic in laboratory animals, and several studies suggested a weak association between certain cancers and chlorinated surface water. US EPA ↗
  • Government sourceAn EPA fact sheet says the EPA and CDC believe the benefits of drinking water disinfection outweigh the potential risks from disinfection byproducts. US EPA ↗

Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.

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