The two most important well tests are:
Coliform Bacteria and Nitrates
Bacteria Coliform bacteria are microorganisms found in the intestines of warm-blooded
animals as well as in soil, on vegetation, and in surface water runoff. Finding coliform bacteria in a water supply is an
indication that there is a potential for disease-producing organisms to be present also.
washed into the ground by rain or melting snow are usually filtered out as water percolates through the soil. However, poorly-constructed
or unsealed wells, fractured rock outcroppings, sinkholes, and quarries may provide a path for coliform bacteria to enter
Once in the groundwater, bacteria can easily pollute drinking water used by private well owners.
Other bacteria, viruses and parasites, which can cause illness, can be in water containing coliform bacteria.
water drawn from private wells should be tested for the presence of bacteria at least once a year or any time there is a change
in taste, odor, color or appearance of the well water.
Iron and sulfur bacteria may also be present in well water.
Although not a health threat, these two types of bacteria can make water smell and taste bad and plug or corrode plumbing
equipment. The State Laboratory of Hygiene offers a test to detect iron bacteria. Some private laboratories Nitrate Although nitrate is found naturally in many types of food, high levels in drinking water pose a serious
acute health threat for infants less than six months of age. Nitrate is changed to nitrite in the stomachs of small infants.
The nitrite then interferes with the blood's ability to carry oxygen, and symptoms of suffocation or blue baby syndrome
can occur. This problem generally does not affect older children or adults. Research is underway to ascertain if nitrate causes
Sources of nitrate include fertilizer infiltration in agricultural areas, animal feedlots,
sewage absorption fields, municipal and industrial wastewater, urban drainage and decaying plant debris. Underground soil
and bedrock structure and the direction of groundwater flow influence when and where nitrate is found. In some areas nitrate
contamination may be associated with other groundwater contaminants.
A nitrate test is recommended for all wells
and is essential for wells serving infants under six months of age. The State Laboratory of Hygiene as well as private laboratories
certified by DNR can test water for the presence of nitrate. If the levels are over 10 mg/l (milligrams per liter or parts
per million expressed as "N"), the water should not be fed to infants under six months of age, or used to prepare
formula. Nitrate is not believed to be a health concern for a pregnant woman or her fetus. Adults concerned with the yet incomplete
and inconclusive research results regarding chronic illness, may wish to reduce consumption of water high in nitrate.
If nitrate levels are less than 5 mg/l, retesting every few years should be adequate. If the results are between 5
and 10 mg/l, more frequent, perhaps annual testing can be considered to monitor fluctuations in nitrate concentration. Concerns
about seasonal concentration fluctuations can be satisfied by quarterly testing. If additional sources or amounts of nitrate
occur in the nearby area, also consider retesting for nitrate.Chlorinating Your Well