How a Water Well Works
Other People Are Reading
-
Finding Water Underground
-
Pumping water out of a private well is how more than 15 million households in the United States get their water. Most rural homes do not have access to public water systems and must pump water from a well that has been drilled, driven or dug somewhere on their property. The depth and type of well depends on the depth of the ground water (or water table). The depth of the ground water depends on annual rainfall, temperature, ground composition and plant coverage in the area. The water table is where dense layers of rock prevent rainwater from continuing downward after it is absorbed by the ground. Water wells tap into this supply of fresh ground water and bring it to the surface.
Types of Water Wells
-
Wells are drilled into bedrock to depths between 100 and 400 feet until a fracture in the bedrock that contains ground water is intersected. In areas where the water table is closer to the surface, wells are driven instead of drilled to depths between 30 and 50 feet. Then pumps are used to pull the water up. Where the water table is close to the surface, a well can be dug by hand and water pulled to the surface using a rope and bucket. There is a higher risk of water contamination with shallow wells--products used on the ground surface can leach through the soil and enter and contaminate the well water.
-
Well Construction
-
A plastic or metal pipe casing that extends about two feet out of the ground identifies the location of a private water well. Driven wells have a larger diameter casing than drilled wells, making them easily disguisable from the surface. The larger diameter allows for a water storage reservoir.
Either way, the casing extends about 18 feet into the ground. Lengths of metal drop pipe with at least a two-inch diameter are placed inside the casing and extend into the ground as far as necessary to reach the water table. The water is pumped out of the ground, up through this metal pipe and into a holding tank. The holding tank in most homes is a pressure tank that contains a bladder inside of its metal casing. The pressure created by the inner bladder helps the water move throughout the home. When a faucet is turned, it uses the water in the pressure tank. As the tank empties, it triggers the water pump to turn on again, refilling the pressure tank. When the pressure tank is full, the pump turns off. Water wells function for about 20 years.
-
References
Resources
- Photo Credit Julia Fuller
