Public water systems are tested regularly for a variety of contaminants, but if you have a private well, routine testing is up to you. The Minnesota Department of Health and Dakota County recommend that well owners annual test drinking water from private wells.
Why should I test my well water? You may discover problems and contamination before their impact is substantial by routinely testing your water. Water testing is an inexpensive and effective way of assuring a safe and healthy water supply.
State and local health authorities recommend that private drinking water supplies are tested annually for total coliform bacteria and nitrate. Well owners may also consider a pesticide screen and immunoassay screen to confirm pesticides and breakdown products of pesticides in a water sample.
Information about your water supply's construction and maintenance, and your observations of its apparent quality (taste, odor, color, sediment, cloudiness, scaling, foaming, etc.), is important.
Common Contaminants include coliform bacteria, nitrate, and pesticide.
Coliform bacteria in your water supply may indicate fecal contamination and the presence of disease-causing microorganisms. The water supply should be disinfected and retested. If the bacteria persist after repeated disinfection treatments, contact the Water Resources Department for recommendations.
Nitrate is derived naturally from air, soil, rock, and plants in low concentrations. High concentrations in groundwater are often associated with human and animal wastes, fertilized and irrigated crops, and landfills. High nitrate concentrations in your water supply may indicate the presence of other contaminants that have not yet been tested or detected.
What is a safe level of nitrate in my well water? A water supply with a concentration of nitrate of more than 10 milligrams per liter indicates a significant risk to infants six months of age and younger. Infants consuming water and water-prepared formula and food containing more than 10 milligrams per liter of nitrate may be prone to methemoglobinemia or "blue-baby" disease.
Older children and adults can ordinarily tolerate higher levels of nitrate without acute disease symptoms. Boiling water that is high in nitrate only increases its concentration and does not make the water safe to drink.
Pesticides A
pesticide screen is a relatively low cost and highly sensitive technique to detect the presence of various groups of pesticides in water. It does not indicate which specific pesticide(s) within a group may be present. The test will confirm the presence of pesticides, within the groups tested, at concentrations above a specified limit.
The immunoassay may indicate the presence of some of the pesticide breakdown products within a particular group. Dakota County offers a combination of the following two pesticide immunoassay screens:
- Triazine screen: This test will indicate the presence of common triazine herbicides, including atrazine (AAtrex), cyanazine (Bladex), and simazine (Princep).
- Lasso/Dual/Acetochlor screen: This test will indicate the presence of alachlor (Lasso), metolachlor (Dual), or acetochlor (Harness).
Herbicides most commonly found in Dakota County private wells include: alachlor, metolachlor, atrazine, cyanazine, and acetochlor or their breakdown products.