A Guide To Water Well Casing and Screen Selection   -   5

3.4  Steel

By far most common casing and screen material is steel. Steel is easily formed into tubes, the ideal casing and screen configuration. When exposed to the atmosphere, water or soils, steel builds up a protective oxide coating which assures long life under mildly corrosive conditions. Under more extreme conditions, steels with special chemistries or alloys, such as the stainless steel grades, are available for greater life or permanent protection. Steel possesses the high yield and tensile strengths required for water well use. Of particular importance are the characteristics of elasticity and resiliency inherent in steel. Casings and screens may be subjected to underground external forces after installation. Earthquakes or subterranean earth movements tend to displace them. Steel permits absorption of many forces with maintenance of structural integrity.

Another important quality of steel is its weldability. This facilitates proper field installation.

3.5  Non-Ferrous Materials

In some areas, non-ferrous materials have been used with some success in wells. The most common are cement, plastic and fiberglass. Concrete casing can be used in some shallow installations, but its weight, difficulty in handling and special connecting-joint requirements, have rendered it impractical for general use.

Plastic has been used successfully in shallow domestic wells up to 8 inches in diameter. Connection, collapsing and tensile strength requirements are relatively modest in such installations. Plastic has not yet been found to be a suitable material for large diameter or deep wells because of cost and strength considerations.

Fiberglass has found use in some areas where waters are known to be corrosive. Again, connecting-joint limitations have restricted its use to shallow and medium depth wells. While mechanical joints designed for this end use have been adequate for installation purposes, they have been known to present difficulties in well rehabilitation. Fiberglass is also costly, particularly for the larger diameter, heavier wall fiberglass tubes required in high production wells.

*See Appendix II.

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