Why Does a Sprinkler System Well Need Casing?

Design

• Wells are often sited above aquifers, which are large underground reservoirs. Aquifers are tapped from above. Drills penetrate layers of sand, gravel, rock and clay until they hit water. Most water in wells does not come from the bottom of the well. Instead, water drains into the well shaft from openings along the shaft sides. The bottom of the well is capped and a pump is placed near the bottom. The pump moves the drained water from below to above ground. Casings and screens are used to hold back sand and debris while still allowing water to penetrate into the shaft.

Slotted Casings

• Slotted casings are placed along the sides of wells. These casings are constructed of heavy plastic, such as PVC, and feature slots that allow water to enter the well's body. The PVC casing's interior is lined with wire mesh to prevent fine grains of rock and grit from entering the usable water. The casing provides the rigidity needed to keep the well from collapsing inward.

Blank and Bottom Casings

• Large-scale wells employ blank casings. These wells can be very deep and must penetrate layers of different rock material. Blank casings are not slotted. Instead they serve as a solid wall of material for sub-surface layers high in sediment. Screens and slotted casings are placed above or below blank casings to allow water infiltration.

  The sump area is located at a well's bottom. This area is below the reach of the pump and serves as a collection point for silt and debris. The casing in this region of the well is solid, not slotted, but is constructed of the same durable PVC material. A capped bottom ensures that additional silt doesn't enter the well from below. Casings provide both a protective layer and a suitable deposit area for well debris.

Considerations

• PVC material is well-suited for wells because the material is durable and doesn't leach chemicals into water. This may not seem important for sprinkler systems, but crops can be subject to contamination from chemicals. High salt and boron levels can lead to crop failure.