Homeowners in many parts of the United States do not have access to city water supplies and instead must rely on well water. A number of factors ranging from aquifer depth to soil contamination can impact the depth of a well. State rules and different types of terrain also affect the average depth of wells in all parts of the nation.
Subterranean rocks, sand and gravel act as natural filters for water that seeps through soil from ground level. Some water accumulates in gaps between the rocks and gravel and geologists refer to these water pockets as aquifers. Aquifers are found at varying depths below the Earth's surface. Some aquifers are within a few feet of ground level, while others are hundreds or even thousands of feet below the surface. Anyone wishing to drill a water well must drill sufficiently deep to strike an aquifer.
The western section of Colorado includes mountainous terrain and, according to the researchers at the University of Colorado, wells in this region are typically 350 feet deep. In the eastern part of the state, well depths average 300 feet. Researchers at the University of Pennsylvania found most wells in that state are at least 100 feet deep. The federal Water Systems Council estimates that most wells in the United States are between 100 and 500 feet deep. However, the council reports that wells in some areas are 1,000 feet deep.
While few states have laws pertaining to well depths, many states have laws pertaining to the placement of wells in relation to septic systems and other possible sources of contaminants. In Pennsylvania, homeowners cannot dig wells within 50 feet of septic tanks or sewers. In parts of Illinois, homeowners must place wells at least 75 feet from septic distribution lines. In New York state, you cannot drill a well within 300 feet of landfills and other hazardous sites. Therefore, while the shallowest point of an aquifer may pass within 100 feet of your house, you may have to dig your well where the aquifer sits deeper underground.
Laws in New York and many other states are designed to conserve water and protect homeowners. In many states, you must hire a certified driller to construct your well and the driller must test the water pressure before installing the well. Most states have rules pertaining to maximum pressure levels. If pressure levels are too high, your well will quickly run out of water and the ground beneath your home could sink. Therefore, you must also take pressure levels into account when you drill a well.