Glossary for Safe Drinking Water Act

561 FW 4
Originating Office
Infrastructure Management Division

Action level. An action level is the concentration of a contaminant which, if exceeded, triggers treatment or other requirements that a water system must follow. The term “action level” is not the same as a Maximum Contaminant Level (MCL). Other examples of an action level include, but are not limited to, a concentration at which a remediation action is triggered, or a situation where a percentage of households affected with high lead concentrations triggers action.

Community Water System (CWS). (See figure under “public water system.”) A community water system:

(1) Serves at least 15 service connections used by the same year-round consumers, or

(2) Regularly serves at least 25 of the same year-round consumers.

Contaminant. A contaminant is any physical, chemical, biological, or radiological substance or matter in water. The U.S. Environmental Protection Agency (EPA) regulates some contaminants and sets monitoring requirements for MCLs, action levels, and treatment technologies. Entities with primacy have responsibility for enforcing the Safe Drinking Water Act (SDWA) and may set more stringent requirements.

Disinfection. Disinfection is a process that inactivates pathogenic organisms in water by adding chemical oxidants or equivalent agents.

Filtration. Filtration is a process for removing particulate matter from water by passing the water through porous media.

Fluid. A fluid is any material or substance that flows or moves, whether in a semisolid, liquid, sludge, gas, or other form or state.

Groundwater Under the Direct Influence of Surface Water (GWUDISW). The SDWA was amended to require all States and entities with primacy to establish a methodology for determining if groundwater systems within their jurisdiction are under the direct influence of surface water. GWUDISW and surface water regulations are site-specific and should be addressed with the assistance of the Regional Environmental Compliance Coordinator (RECC).

Hauled water system. Facilities and boats use these systems when they are not directly supplied water by municipalities or wells. They use onsite tanks to store and distribute water to the facility or boat.

Lead and Copper Rule. EPA’s Lead and Copper Rule implements the part of the SDWA specific to limiting exposure to lead and copper.

Maximum Contaminant Level (MCL). An MCL is the maximum permissible level of a contaminant in water in a public water supply system. EPA’s MCL concentrations may be found on their website. Entities with primacy (i.e., States) may have more stringent requirements.

National drinking water standards. EPA establishes and updates the following two categories of national drinking water standards:

(1) Primary drinking water regulations. Primary drinking water regulations are legally enforceable standards expressed as MCLs or as treatment techniques that apply to public water systems.

(2) Secondary drinking water standards. Secondary standards are non-enforceable guidelines regulating contaminants that may cause cosmetic or aesthetic effects (such as taste, odor, or color) in drinking water. While secondary standards are recommendations and are not enforceable, some States may choose to adopt them as enforceable standards.

Non-Community Water System (NCWS). An NCWS is classified as either transient or non-transient. These categories are based on the number of people the system regularly serves and the period of time over which they are served. (See figure under “public water system.”)

Non-Transient Non-Community Water System (NTNCWS). An NTNCWS regularly supplies water to at least 25 of the same people at least 6 months per year, but not year-round. (See figure under "public water system.")

Potable water. Potable water is water that is fit for humans to drink or to prepare food.

Primacy. EPA delegates primary enforcement responsibility (also called primacy) for public water systems to States, territories, and Tribes if they meet certain requirements set by 40 CFR 141. An entity with primacy is the agency with primary responsibility for implementing the SDWA.

(1) Most States and the U.S. territories have been approved to exercise primary responsibility in their jurisdictions. Exceptions are the State of Wyoming and the District of Columbia, which are implemented by EPA. The Navajo Nation has been approved for primary responsibility for implementing SDWA on their lands, but EPA implements SDWA on all other Tribal lands.

(2) Entities that have primacy may establish drinking water regulations, monitoring schedules, and reporting requirements more stringent than, or in addition to, those in the EPA regulations. Project Leaders/Facility Managers should ensure that they are complying with their jurisdiction’s regulations on drinking water in addition to the requirements established by the SDWA.

Public water system. A public water system has 15 or more service connections OR serves an average of 25 or more people at least 60 days a year. A public water supply system is classified as a community water system or a non-community water system. See figure below. Water systems that do not meet these criteria are Non-Public Water Systems.

Figure: Public Water Supply Systems

Regulated contaminant. Regulated contaminants are chemicals for which the regulated authority (e.g., EPA, a State) has set enforceable monitoring requirements and that have MCLs, action levels, or treatment technologies associated with the monitoring requirements.

Regulatory agency. The regulatory agency is EPA or the State, territory, Tribe, or local authority responsible for enforcing the SDWA.

Safe Drinking Water Act (SDWA). In 1974, Congress passed the SDWA, which directs EPA to set legal limits for more than 90 contaminants in drinking water. The legal limit for a contaminant reflects the level that is protective of human health and that water systems can achieve using the best available technology. EPA rules also set water testing schedules and methods that water systems must follow.

Sanitary survey. A sanitary survey is a comprehensive onsite review of the water source, facilities, equipment, operations, and maintenance of a public water supply system to evaluate the capabilities for producing and distributing safe drinking water (see 40 CFR 141). The entity having primacy conducts the sanitary survey following the standards established by that entity. Typically, the person conducting the survey must be a certified water system operator with a current State license and specialty training related to sanitary surveys.

Service connection. A service connection is a location where potable water is delivered from the supply or distribution system to a building. Each service supply to a unique or distinctive facility, such as to a visitor center, office building, or an RV pad, is considered a separate service connection. Each building supplying potable water is considered to have a unique service connection. Service connections are important for determining the public water supply system classification. Entities with primacy may promulgate additional definitions of service connections for their jurisdictions, and Project Leaders/Facility Managers should be aware of specific requirements for their locations.

Surface Water Treatment Rule. The Surface Water Treatment Rule applies to all public water systems using surface water sources or ground water sources under the direct influence of surface water (GWUDI) and requires water systems to filter and disinfect surface water sources.

System operator. EPA requires system operator training and certification programs for community water systems and non-transient non-community water systems. Entities with primacy administer these programs and may be more stringent than EPA. These entities determine the qualifications for system operators for water systems using surface water or ground water under the direct influence of surface water.

Transient Non-Community Water System (TNCWS). A TNCWS provides water to 25 or more people for at least 60 days/year, but not to the same people and not on a regular basis (for example, campgrounds).  Potable water on vessels must meet the minimum TNCWS requirements described in Table 4-2 in 561 FW 4. (See figure under “public water system.”)

Well. A well is a bored, drilled, driven, or dug hole, with a depth greater than the largest surface dimension.

Well injection. Well injection is placing fluids through a bored, drilled, driven, or dug well.