The design and construction of a well should be adapted to the geologic and groundwater conditions existing at the site of the well. The purpose is to utilize fully every natural sanitary protection afforded thereby. The installation should be designed to facilitate any supplementary construction that may be required to provide a sufficient and safe water supply, and to conserve the groundwater resource.

In selecting the type of well to be constructed, these objectives should be attained:

1. The well be adequate in diameter and depth to obtain the water available from the water-bearing formation in which the well is to be completed.
2. The well should be so designed that it will seal off water-bearing formations that are or may be contaminated.
3. The well should be designed to leave no unsealed opening around the well which could conduct surface water, contaminated groundwater or undesirable groundwater vertically to the intake portion of the well.
4. The materials that are to be a part of the permanent well should be durable.

The well structure should be visualized as consisting of two main elements. One of these is the portion of the well that functions both as a housing for the pump and as a conduit through which water flows upward from the aquifer to the level where the pump is set. This is commonly the cased portion of the well. The other main element is the intake section of the well (the screened section of a well completed in an unconsolidated sand aquifer, or the open borehole in a consolidated rock aquifer).

When selecting the type of pipe for well casing, it is necessary to consider the stress to which the pipe will be subjected during the installation and to consider the corrosiveness of the water with which it comes in contact.