Drinking Water Standards

Federal drinking water standards are in force for public water systems. Private water supplies are not subject to these standards.

Public Water Systems

The term "public water system'' means a system for the provision to the public of water for human consumption through pipes or other constructed conveyances, if such system has at least fifteen service connections or regularly serves at least twenty-five individuals.(1)

The federal government has established regulatory limits (standards) on over 100 chemical and microbial contaminants in drinking water. These have their origin in the Safe Drinking Water Act (SDWA), which governs public water systems. Many states have established their own standards, which must be at least as stringent as the federal standards.

The U.S. Environmental Protection Agency (EPA) sets two types of standards:

Primary standards are set to provide the maximum feasible protection to public health. They regulate contaminant levels based on toxicity and adverse health effects. The goal of standard setting is to identify maximum contaminant levels (MCLs) which prevent adverse health effects. (2)

Secondary standards regulate contaminant levels based on aesthetics such as color and odor, which do not pose a risk to health. These secondary maximum contaminant levels (SMCLs) are guidelines, not enforceable limits. They identify acceptable concentrations of contaminants which cause unpleasant tastes, odors, or colors in the water. SMCLs are for contaminants that will not cause adverse health effects.(3)

Public water suppliers are required to monitor the quality of the water they supply.(4) Consumers must be notified if a primary standard is exceeded.

Health Advisories are guidance values based on non-cancer health effects for different durations of exposure (e.g., one-day, ten-day, longer-term, and lifetime). They provide technical guidance to EPA Regional Offices, State governments, and other public health officials on health effects, analytical methodologies, and treatment technologies associated with drinking water contamination. (5)

EPA maintains Webpage tables of the Primary and Secondary standards and Health Advisory guidance values. There are consumer fact sheets on each of the contaminants for which there are primary standards.

Private Water Supplies

Users of private wells or other private water sources are solely responsible for monitoring and maintaining the quality of their water supply. Some state or local health authorities regulate private water sources. Check with your local health department.(4)

Farm*A*Syst and Home*A*Syst are programs which support the voluntary efforts of farmers, ranchers, and urban and rural residents in protecting the quality of the environment. Their websites include materials for self-assessment of water quality. They also maintain a directory of state contacts to help you.(6)

If you you are looking for more information on specific water laws, click here.

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  1. 42 U.S.C. 300f(4)
  2. Drinking Water Standards. Water Quality Association, 1995. http://www.wqa.org/WQIS/Glossary/Drinking-Water-stds.html
  3. Aesthetic Water Qaulity Problems. Water Review Technical Brief, 1991 v. 6 no. 4. ,http://www.wqa.org/WQIS/aesthetics.html
  4. Water Quality Association. Water: From Its Source to OUr Taps. Water Review Technical Brief, 1991 v.6 no3. http://www.wqa.org/WQIS/Water-Source-Taps.html
  5. U.S. EPA. Office of Water. 1996. Drinking Water Regulations and Health Advisories. EPA 822-B-96-002 http://www.epa.gov/OST/Tools/dwstds-s.html
  6. Farm*A*Syst/Home*A*Syst home Page. http://www.wisc.edu/farmasyst/

URL References:

U.S. EPA. Office of Water. 1996. Drinking Water Regulations and Health Advisories. EPA 822-B-96-002 http://www.epa.gov/OST/Tools/dwstds.html
Drinking Water and Health. U.S. EPA Office of Groundwater and Drinking Water, Rev. 9/26/97. http://www.epa.gov/OGWDW/dwhintro.html
Tools for Farmers and Ranchers, May 1997 http://www.wisc.edu/farmasyst/tool1.html
Home*A*Syst Home Page, University of Wisconsin, Madison, May 97. http://www.wisc.edu/homeasyst/index.html
Farm*A*Syst Map of Contacts, University of Wisconsin, Madison, May 97. http://www.wisc.edu/farmasyst/map.html

This page was prepared by T.L. Pedersen and L.A. Kleinschmidt, UCD EXTOXNET FAQ Team.
June 1997