There are more than 15 million homes in America with their own water wells. More than half of the nation's drinking water is from municipal and private wells. Some estimates are that 6,000 new wells are completed each week in the United States. Virtually all these wells are drilled wells. Few people give any thought to how you make a deep vertical hole in sand or in solid rock, how the drilled pieces of rock are removed from deep below the surface, or how drillers stop the hole from collapsing before the casing (liner) is put in.
Great skill is needed to guide and control a water well drill as it penetrates sand, gravel, clay and solid rock formations deep underground. The drill rods can weigh several tons. If the drill pushes too hard or turns too fast, the drill bit will wear out; if it does not push hard enough, it won't penetrate the rocks. There often are several rock layers in a single well; each may need different drilling pressures. Once water is encountered, the driller will need to keep a close watch on the drilling process. By comparison, dentists have only one material to drill, a light can be shined to the bottom of the hole, pieces can easily be washed out and the dentist works in an air-conditioned room.