Contaminants in water may be health-related (e.g., bacteria) or a nuisance (e.g., hardness causing scale) and can come from a variety of sources.
Some contaminants originate from geology, the sediment or rock where the water is stored. Others are a result of land usage or activities on the earth's surface, such as lawn fertilizer, animal waste, or chemical spills.
Proper construction of a well can protect household water quality by preventing surface water, which may carry many contaminants, from entering the groundwater supply. Wells should be constructed with proper casing, grout seal, and a sealed well cap. Contamination sources, such as livestock and septic systems should be at least 50 feet away from the well head.
Treatment devices and plumbing components can also influence water quality by adding contaminants or changing water chemistry.