Bacteria

E. coli is a type of bacteria that can indicate your water has been in contact with human or animal waste. Generally, E. coli is not harmful, however if it's found in your water, it could mean that there are other, more harmful, bacteria and viruses present.

Bacteria that are washed into the ground are usually filtered out as the water goes through the soil and into the groundwater. However, improperly constructed wells, or wells that are cracked, unsealed, or otherwise damaged, can provide a path for bacteria and other microorganisms to enter groundwater and contaminate your drinking water. Intrusion of bacteria into damaged wells is at a greater risk during instances of heavy rainfall, flooding, and hurricanes.

If E. coli can get into your well water, it is more likely that other organisms, such as bacteria and viruses that do cause disease, can also get in. Therefore, the presence of E. coli in your well means that it is time to take action to keep your well water safe.

While private wells are not currently regulated by the US EPA, EPA sets guidelines for public piped water systems to be free from E. coli in a 100-mL sample. If any E. coli in a water sample is detected, action should be taken to improve the safety of your well water.