New Well
Sampling Program

In order to assure that the citizens of South Dakota are provided with a good quality water supply, the Centennial Environmental Protection Act of 1989 requires that all new domestic wells drilled in South Dakota are tested for bacteria and several selected chemicals. The test results, which provide a general indication of water quality, are for your information and allow you to judge for yourself as to the general quality of the water. Here is an explanation of your test results:

Bacteriological Analysis (Safe or Unsafe)

Learn how to take bacteriological samples (pdf)

If your bacteriological analysis is determined to be unsafe for drinking purposes, it means there are organisms of the coliform group are present in your water. These organisms are characteristic of sewage, sewage-like materials and surface drainage. Until your well is tested and found to be safe, the water should be boiled before being used for drinking purposes.

Shallow and deep wells are most often contaminated by means of surface water which enters around the pump, through the well cover, or through the upper few feet of the well casing.

Wells are sometimes terminated in pits for the purposes of preventing freezing during cold weather. These pits will often collect surface waters which may enter the well by overflowing into the casing or by seeping down the outside of the casing and then into the water bearing formation. It is possible for water to seep down the outside of the casing a considerable distance without the bacteria being filtered out, since the space between the drill hole and the casing often has not been completely filled in. From a sanitary viewpoint, well pits are not desirable.

Disinfecting Your Well (pdf)

It is recommended that the bacteriological quality of the water be retested at least annually. After heavy rains, snow melt, or flooding in the area of your well, a sample of water should be submitted for at least a bacteriological and nitrate analysis


Nitrate in excess of 10 mg/L (as nitrogen) is of health significance to infants of six (6) months of age or less, and pregnant women. High nitrate water should not be used for infant feeding or formula preparation. Nitrate cannot be removed or reduced by boiling. Boiling will actually increase the concentration of nitrate in the water.


Sodium may be health significance to persons on a low salt diet. Most home water softeners are ion exchange (zeolite) water softeners. The sodium content is increased when water is passed through this type of softener. People on low sodium diets should consult their physician as to how much water may be consumed.


Water with a sulfate content in excess of 250 mg/l may have a bitter taste and have a laxative effect on persons not adapted to the water. Sulfates may contribute to odor problems. The sulfate content can be reduced in a private water supply through distillation or reverse osmosis treatment.


Conductivity measures the ability of water to conduct an electric current. It is related to the type and amount of dissolved chemicals in the water. In general, water having a conductivity of less than 1000 microohms is slightly mineralized, but should be suitable for human consumption. It may have some hardness and it is possible to have taste and odor problems. Depending upon the particular chemicals dissolved in the water, these problems may become more pronounced with increasing conductivity to the extent that levels greater than 2000 microohms may make the water objectionable to human use.