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Background on Drinking Water Standards in the Safe Drinking Water Act (SDWA)

Summary of SDWA Related to Contaminants:

  • Congress enacted the Safe Drinking Water Act (SDWA) in 1974 and amended and reauthorized it in 1986 and 1996.
    • Main federal law that ensures the quality of Americans' drinking water
    • Authorizes EPA to set national standards for drinking water to protect against health effects from exposure to naturally-occurring and man-made contaminants
  • Drinking water standards only apply to public water systems (not individual private wells).
  • EPA works with states, localities, and water suppliers who carry out these standards.

Drinking Water Standards Apply to Public Water Systems:

  • Public water systems are those having at least 15 service connections or serve at least 25 people for at least 60 days a year.
  • Over 150,000 public water systems across the U.S. serve more than 300 million people.

Three Types of Public Water Systems: 

  • Community Water Systems (CWSs)
    • Provide water to the same population year-round (for example: homes, apartment buildings)
    • Approximately 52,000 systems serving the majority of the U.S. population
  • Non-Transient Non-Community Water Systems (NTNCWSs)
    • Provide water to same people at least six months a year, but not all year (for example: schools, factories, churches, office buildings that have their own water system)
    • Approximately 85,000 systems
  • Transient Non-Community Water System (TNCWS)
    • Provide water where people do not remain for long periods of time (for example: gas stations, campgrounds)
    • Approximately 18,000 systems
Drinking water standards may apply differently based on type and size of public water systems.

SDWA Processes Involving Drinking Water Contaminants:

    • Requires EPA to develop a list of unregulated contaminants that are known or may occur in drinking water
    • Publish every five years
    • Requires EPA to decide whether to regulate at least five CCL contaminants with a drinking water standard every five years
    • Specifies three criteria (adverse health effects, occurrence in public water systems, meaningful opportunity for health risk reduction)
    • Requires EPA to establish criteria for a program to monitor at least 30 unregulated contaminants every five years
    • If EPA decides to regulate a contaminant via the regulatory determination process, the Agency has 24 months from the time of the determination to propose a regulation and 18 months from the proposal to finalize the regulation.
    • The SDWA requires evaluatation of a number of factors in the standard setting process.
    • EPA is required to review each standard every six years and, if appropriate, revise the standard.
    • Any revision must maintain or improve public health protection.
    • If a regulation is revised, EPA goes through the standard setting process again and evaluates a number of factors.
    • Requires EPA to assemble and maintain a national drinking water contaminant occurrence database using information for both regulated and unregulated contaminants in public water systems

For a more detailed summary of how these various drinking water contaminant provisions of SDWA work together, read How EPA Regulates Drinking Water Contaminants.

For more information on broader provisions of SDWA, select the Safe Drinking Water Act website.