Test your well water after flooding

After heavy rains or flooding, it is a good time to inspect your private 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

Soil usually absorbs drinking water contaminants 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 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.
• Follow the handling and sanitizing instructions, as false-positive results can occur if the faucet isn't sanitized before sampling.

Well construction

Minnesota has had an established well code standardizing well construction since 1974.

Code requirements:

• 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.
• A well ID tag should be attached to the pipe, though some older wells may not have one.

If applicable to your area, some wells have a gas vent from the cap with a mesh screen.

When inspecting your well, look for:

• Cracks in the electrical conduit piping.
• Loose well pipe sanitary cap.
• Worn mesh screen on the gas vent (if applicable). 

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.

Videos

• Groundwater and private wells (2026; 01:49)
• Private well construction (2026; 02:28)
• Well water contamination (2026; 02:13)