According to the Center for Disease Control (CDC), the United States has one of the safest drinking water supplies in the world. Most Michigan residents’ water is likely meeting chemical and biological safety standards.

However, contamination can (and does) occur. It is vital for you to understand how it happens and what types of pollution may be present in your system.

In private wells, contamination almost always occurs at the water source.

Contaminants may be introduced through several routes, including from naturally occurring minerals, local land use practices, malfunctioning wastewater systems, improperly stored chemicals or hazardous wastes, and other sources.

Contamination from a single well can potentially affect an entire aquifer and all wells within the area. Properly disposing of chemicals and waste is vital for community health.

According to the CDC, the most common outbreak-causing biological contaminants in wells include:

  • Hepatitis A virus
  • Giardia
  • Escherichia coli (E. coli)
  • Campylobacter
  • Shigella
  • Cryptosporidium
  • Salmonella

Chemical contaminants, such as arsenic, gasoline, nitrate, phenols, and selenium, can also be present but are less likely to cause outbreaks.

Find out if your well may be vulnerable to contamination. Check out the Michigan Department of Environmental Quality (MDEQ) Environmental Mapper.



The CDC recommends checking your well every spring for mechanical issues and testing it at least once a year for specific water quality indicators, including total coliform bacteria, nitrates, total dissolved solids, and pH levels. If you are concerned about other contaminants, you should test for those as well.