A Private well can be a source of clean, drinkable water if it is suitably located appropriately designed, carefully installed, and properly maintained.
Ground water which occurs nearly everywhere is the water from precipitation that falls and fills the spaces between grains of soil or fractures in the bedrock. Reservoirs of sufficient water bearing material are called aquifers. When pumping is started, the water level in the vicinity of the well is lowered. The amount of the drop in the water level is called drawdown. Drawdown is greatest close to the well and decreases to a point where the water level is essentially unaffected. Underneath the ground surface the area of drawdown is called a cone-of-depression however on the surface it is known as the wellhead or area of influence. When pumping water from a well, the direction of ground water flow will always be toward the well. The area of influence may extend as far away as 500-1000 feet and must be protected from any possible contaminants.
As a homeowner with an individual water system it is your responsibility to maintain proper operations and water quality. A private well is an investment; to replace or find another uncontaminated supply is very costly.