Drinking water standards and well water testing results can be hard to understand if they are new to you. Our staff have answered some of your most common questions about nitrate testing and groundwater protection below.

1. What is the drinking water standard for nitrate-nitrogen?

10 milligrams per liter (mg/L) or 10 parts per million, these are equivalent values. This value is often referred to as the drinking water standard, health standard or Maximum Contaminant Level (MCL).

2. Who establishes the drinking water standard for nitrate?

The Environmental Protection Agency (EPA) is a federal agency that is responsible for regulating nitrate in drinking water. You can learn more by reading the EPA’s web page titled Drinking Water Contaminants – Standards and Regulations.

3. What should I do if my nitrate results are between 0 and 4.9 mg/L?

The nitrate level in your water is well below the nitrate health standard for drinking water (10 mg/L). Continue to test your water for nitrate every year or every other year.

Remember, private wells should be tested for bacteria at least once a year. A Minnesota Department of Health certified water testing lab can provide nitrate and bacteria testing services. Search for the lab nearest you.

4. What should I do if my nitrate results are between 5 mg/L and 9.9 mg/L?

The nitrate level in your water is below the nitrate health standard for drinking water (10 mg/L). However, you have a source of contamination that may include contributions from fertilized lawns or farm fields, septic systems, animal waste, and/or decaying plants. Test annually for both nitrate and bacteria.

5. What should I do if my nitrate results are above 10mg/L?

Do not let infants drink this well water. Water with levels over 10 mg/L nitrate is not safe for infants younger than 6 months of age. People with specific metabolic conditions should not drink this water. Steps to take:

  • Retest your well to confirm results (Search for the certified lab nearest you)
  • Install a water treatment unit that reduces nitrate, such as a reverse osmosis system or a distiller, in your house and in other areas where this water is consumed by people or animals.
  • Consider upgrading your well if it was constructed before the mid 1970s.
  • Consider an alternative drinking water source until you can appropriately address the issue.

6. What actions is the MDA going to take to address high nitrate concentrations in groundwater (including drinking water)?

After our agency receives all the well testing results in a township, the data will be analyzed and information about well depth, well age and well construction will be reviewed. In some cases, MDA staff may need to revisit wells to retest and confirm water quality results. After we complete our analysis, we will determine if local nitrate levels meet the criteria for the MDA to take action. If so, the MDA will work with a local advisory group to address the problem. In many cases, the MDA will work directly with farmers to adopt practices on their farms that would decrease nitrate levels in groundwater.

The Nitrogen Fertilizer Management Plan (NFMP) describes the criteria we use to take action and other details about the MDA’s response to nitrate in groundwater.

7. What other state agency has information about drinking water protection?

The Minnesota Department of Health is the lead state agency for drinking water protection. Visit their website, to learn more about their programs and how they work with homeowners to protect public health.

8. Why am I being offered a pesticide analysis of my well? Will everyone receive this analysis?

If nitrate is detected in a water sample from a private well it may indicate that there is a pathway for contamination. If well water is vulnerable to one contaminant, such as nitrate, it may be vulnerable to other contaminants, such as pesticides, because they are both present in agricultural areas.

MDA is currently offering a free pesticide sample to well owners who had detectable concentrations of nitrate in their well water during the Township Testing process.

9. Why does a trained professional need to collect the water sample for pesticide analysis?

A trained professional needs to collect water samples for pesticide analysis to ensure they are collected properly. Specifically that the water sample is not exposed to any contaminants during the collection or transport to the lab. The MDA staff uses established procedures and sampling protocol.

10. What are the next steps?

After the MDA receives all of the well testing results in a township, the data will be analyzed. The results of that analysis will determine the next steps. The MDA’s framework for addressing nitrate in groundwater is outlined in the Nitrogen Fertilizer Management Plan (NFMP).