Quick facts
- Heavy rains and flooding can help bacteria enter well water.
- Inspect your well for cracks and other deterioration around the well cap.
- Have your water tested by a certified lab.
If you have a private well, after heavy rains or flooding, it is a good time to inspect your well and have your drinking water tested at a certified laboratory. Properly constructed wells can help prevent outside water, debris, and rodents from entering your drinking water source, but small issues can sometimes go unnoticed.
What to test for and why
Drinking water contaminants are usually absorbed by the soil before they enter a well. But if a well isn’t sealed or constructed correctly, contaminants can enter the system.
Severe weather and flooding can make these issues worse.
Private wells should be tested annually for coliform bacteria. This bacterium is harmless on its own, but it can indicate the presence of other potentially dangerous bacteria in your water, such as E. coli.
If any foreign material, such as rodents or animal feces, enters your well, a coliform bacteria test can indicate whether further investigation is needed.
To collect a water sample, work with a certified water-testing lab near you. They will provide instructions on how and when to test your water.
Make sure to follow the handling and sanitizing instructions, as false-positive results can occur if the faucet isn't sanitized sufficiently before sampling.
Well construction tips
Minnesota has had an established well code since 1974, standardizing well construction.
- A well must have a sanitary well cap.
- The electrical conduit must also be sealed into the cap.
- The cap must be at least 12 inches above the ground surface in case of flooding.
- There should also be a well ID tag attached to the pipe, though some older wells may not have these.
If applicable to your area, some wells have a gas vent from the cap with a mesh screen.
When inspecting your well, ensure all of these features are met. Some things to look for are:
- A crack in the electrical conduit piping.
- The sanitary cap is loose from the well pipe.
- Or the mesh screen on the gas vent (if applicable) is badly worn.
Any of these can create opportunities for contaminants to enter your well. If you have a problem with your well, contact a licensed well driller for an inspection and cost estimate.
Learn more about drinking water contaminants.
Find out about the Private Well Education Program.
Minnesota Department of Health resources
Reviewed in 2022