Well Casings

A well casing is pipe, inserted into a well after it is drilled to its final depth, to prevent the collapse of the borehole and to help keep out contaminants. For more information, see the "Private Drinking Water" computer program, available from the Agricultural Engineering Department, Purdue University, West Lafayette, IN 47907.

Pathways for Contaminant Entry into an Unprotected Well

Improperly Cased Wells

Check the condition of your well casing by listening for water running down in the well. If you do hear water, there could be a crack or hole in the well casing. If you can move the casing around by pushing against it, you may also have a problem with your well casing's ability to keep out contaminants.

Depth of Well Casing

The well casing should extend at least 30 feet below the water table. This ensures that surface water is filtered through at least 30 feet of soil before entering the well.

Water Table

Water Table
The very top of the zone of saturation, or the level of underground water. Although some water can be found a few centimeters above this level due to capillary action, almost all groundwater is at or below this level. The water table can rise or fall, depending on rainfall, evaporation, or pumping action. High water tables can be a problem since surface contaminants do not have as far to travel to reach the groundwater and are therefore not filtered as well.

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