Where Does Your Tap Water Come From?
Understanding surface water vs. groundwater sources and why it matters for quality.
Two sources, different characteristics
Surface water (rivers, lakes, reservoirs) serves about 68% of Americans. It requires more treatment (filtration, disinfection) because it is exposed to the environment. It tends to have higher organic content, leading to more disinfection byproducts. Hardness depends on watershed geology.
Groundwater (wells, aquifers) serves about 32% of Americans. Natural filtration through rock and soil means less treatment is needed for particles and bacteria. However, groundwater often has higher mineral content (hardness), and can contain naturally occurring arsenic, radium, or uranium depending on geology.
Why it matters
Your water source determines which contaminants are most likely and what treatment you might need. Surface water cities tend to have more chlorine taste and DBP concerns. Groundwater cities tend to have harder water and more minerals. Your city page on CheckMyTap lists the specific source.