Where Does Tap Water Come From?
Tap water typically comes from surface water (lakes, rivers, reservoirs) or groundwater (wells, aquifers). It is treated at a water treatment plant where it is filtered, disinfected, and tested for safety before being pumped through a network of pipes to your home. The entire process is regulated and monitored to ensure the water meets safety standards.
Key Takeaways
- Water utilities source water from surface sources (rivers, lakes, reservoirs) or underground aquifers.
- Some cities use desalination (removing [salt](/does-salt-expire) from seawater), though it is energy-intensive.
- Private wells are not regulated by the EPA - owners must test and treat their own water.
Explanation
Water utilities source water from surface sources (rivers, lakes, reservoirs) or underground aquifers. Surface water requires more treatment due to exposure to contaminants. Groundwater is naturally filtered through soil and rock but may contain minerals. Many cities use a combination of sources.
Treatment typically includes: screening (removing large debris), coagulation and flocculation (chemicals cause small particles to clump), sedimentation (clumps settle out), filtration (water passes through sand, gravel, charcoal), and disinfection (chlorine, UV, or ozone kills microorganisms). Some systems add fluoride for dental health.
After treatment, water is stored in reservoirs and towers, then distributed through miles of underground pipes. Water pressure is maintained by gravity (elevated tanks) or pumping stations. The entire system is monitored for quality, and utilities must meet EPA standards and report annual water quality data.
Things to Know
- Some cities use desalination (removing salt from seawater), though it is energy-intensive.
- Private wells are not regulated by the EPA - owners must test and treat their own water.
- Lead can enter water from old pipes between the treatment plant and your tap, not from the source.