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Water Contamination and Diseases

Tap water sometimes gets contaminated with germs and chemicals at high enough levels to make you sick. Learn how public water and private wells get contaminated and how to find out if your water has unsafe levels of germs or chemicals.

Public water is regulated but can sometimes get contaminated

The U.S. Environmental Protection Agency (EPA) regulates drinking water quality in public water systems and sets limits for germs and chemicals in water. However, sometimes unsafe levels of harmful germs and chemicals contaminate public drinking water. The germs and chemicals can get in the water at its source (for example, ground water or water from lakes or rivers) or while water is traveling through the distribution system, after the water treatment plant has already removed germs and chemicals from source water.

EPA requires water utilities to test for and address many germs and chemicals in their drinking water systems. Water utilities are required to tell customers about testing for contaminants and whether they found any unsafe levels of chemicals or germs in the water. Customers are notified through notices of violations and drinking water advisories. Water utilities must also provide their customers with an annual drinking water quality report called the Consumer Confidence Report.

Some people are more likely to get sick from germs and chemicals in water:

  • Infants
  • Young children
  • People who are pregnant
  • Older adults
  • People who have weakened immune systems, such as people living with HIV, getting chemotherapy treatment, or taking transplant medications

How water gets contaminated

Germs and chemicals can get in drinking water at the water’s source or in the distribution system after the water has already been treated. Harmful germs and chemicals can get in the water from many sources, including:

  • Fertilizers, pesticides, or other chemicals that have been applied to land near the water
  • Concentrated feeding operations (large industrial animal farms)
  • Manufacturing operations
  • Sewer overflows
  • Storm water
  • Wildlife
  • Rocks and soil that naturally have chemicals and minerals such as arsenic, radon, and uranium
  • Cracks in water pipes or other problems in the distribution system

Get more information about specific germs and chemicals that most commonly get into water and cause disease, and how to remove them:

Private well owners are responsible for testing their water

Unlike public drinking water supplies, private wells are not regulated by EPA. Owners of private wells are responsible for testing their water to make sure it is safe to drink.

If you have a private well, test it at least once a year for mechanical problems, cleanliness, coliform bacteria, nitrates, and any other germs or chemicals of local concern. Also check your well after flooding or if you suspect a problem (for example, a change in taste or smell). Germs and chemicals can get in wells after flooding, particularly if wells are shallow, were dug or bored, or were covered by floodwater for days or weeks.

If your water is contaminated (has unsafe levels of germs or chemicals), do not drink it and contact your health department for advice about how to make it safe to drink.

If your private well has harmful germs or chemicals in it, your neighbors’ water may also be unsafe to drink. This is because your well is likely connected to the same source of ground water (aquifer).

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