These definitions are not intended to be complete or to have legal force, but rather to help consumers understand drinking water-related terms in the context of their daily lives.
Acoustic Leak Detectors
listen for water leaks in underground pipes.
The level of lead or copper which, if exceeded, triggers treatment or other requirements that a water system must follow.
A natural underground layer, often of sand or gravel, that contains water.
Best Available Technology
The water treatment(s) that EPA certifies to be the most effective for removing a contaminant.
Mix of fresh and salt water.
A group of related bacteria whose presence in drinking water may indicate contamination by disease-causing microorganisms.
Community Water System
A water system which supplies drinking water to 25 or more of the same people year-round in their residences.
The act of meeting all state and federal drinking water regulations.
Transaction in which a private entity makes an up-front payment for the right to operate municipal infrastructure assets on a long-term basis.
Anything found in water (including microorganisms, minerals,etc.) which may be harmful to human health.
Public-private partnership for the operation and maintenance of water and wastewater facilities.
A microorganism commonly found in lakes and rivers which is highly resistant to disinfection. Cryptosporidium has caused several large outbreaks of gastrointestinal illness, with symptoms that include diarrhea, nausea, and/or stomach cramps. People with severely weakened immune systems (that is, severely immuno-compromised) are likely to have more severe and more persistent symptoms than healthy individuals.
Process that removes salt from seawater, turning it into drinking water.
A chemical (commonly chlorine, chloramine, or ozone) or physical process (e.g., ultraviolet light) that kills microorganisms such as bacteria, viruses, and protozoa.
A network of pipes leading from a treatment plant to customers' plumbing systems.
State or EPA permission for a water system not to meet a certain drinking water standard. An exemption allows a system additional time to obtain financial assistance or make improvements in order to come into compliance with the standard. The system must prove that: (1) there are compelling reasons (including economic factors) why it cannot meet a MCL or Treatment Technique; (2) it was in operation on the effective date of the requirement; and (3) the exemption will not create an unreasonable risk to public health. The state must set a schedule under which the water system will comply with the standard for which it received an exemption.
Water that has been treated and is ready to be delivered to customers.
Process in the water and wastewater system that equalizes the flow in peak hours during the day, when customers use the most water.
A microorganism frequently found in rivers and lakes, which, if not treated properly, may cause diarrhea, fatigue, and cramps after ingestion.
The water that systems pump and treat from aquifers (natural reservoirs below the earth's surface).
An EPA document that provides guidance and information on contaminants that can affect human health and that may occur in drinking water, but which EPA does not currently regulate in drinking water.
Pipes, pumps, filtration equipment and treatment plants used for the collection and treatment of wastewater, and treatment and distribution of drinking water.
Mineral-based compounds such as metals, nitrates, and asbestos. These contaminants are naturally-occurring in some water, but can also get into water through farming, chemical manufacturing, and other human activities. EPA has set legal limits on 15 inorganic contaminants.
Information in a corporate responsibility report that reflects the organization's significant economic, environmental and social impacts, or that substantively influences the assessments and decisions of stakeholders.
Maximum Contaminant Level (MCL)
The highest level of a contaminant that EPA allows in drinking water. MCLs ensure that drinking water does not pose either a short-term or long-term health risk. EPA sets MCLs at levels that are economically and technologically feasible. Some states set MCLs which are more strict than EPA's.
Maximum Contaminant Level Goal (MCLG)
The level of a contaminant at which there would be no risk to human health. This goal is not always economically or technologically feasible, and the goal is not legally enforceable.
Tiny living organisms that can be seen only with the aid of a microscope. Some microorganisms can cause acute health problems when consumed in drinking water. Also known as microbes.
Testing that water systems must perform to detect and measure contaminants. A water system that does not follow EPA's monitoring methodology or schedule is in violation, and may be subject to legal action.
Ownership of water and wastewater utilities that provide services to customers that are not subject to economic regulation by the state public utility commissions.
Non-Transient, Non-Community Water System
A water system which supplies water to 25 or more of the same people at least six months per year in places other than their residences. Some examples are schools, factories, office buildings, and hospitals which have their own water systems.
Carbon-based chemicals, such as solvents and pesticides, which can get into water through runoff from cropland or discharge from factories. EPA has set legal limits on 56 organic contaminants.
A State that has the responsibility and authority to administer EPA's drinking water regulations within its borders. The State must have rules at least as stringent as EPA's.
An advisory that EPA requires a water system to distribute to affected consumers when the system has violated MCLs or other regulations. The notice advises consumers what precautions, if any, they should take to protect their health.
Partnership between a municipality that owns the water or wastewater system and the private water company that operates and maintains it.
Public Utility Commission (PUC)
State commission or other entity engaged in economic regulation of public utilities. Also called board of public utilities (BPU) in some states.
Public Water System (PWS)
Any water system which provides water to at least 25 people for at least 60 days annually. There are more than 170,000 PWSs providing water from wells, rivers and other sources to about 250 million Americans. The others drink water from private wells. There are differing standards for PWSs of different sizes and types.
Process to obtain approval for a change in rate that involves filing a petition with a state public utility commission (PUC) or board of public utilities (BPU).
Water in its natural state, prior to any treatment for drinking.
Treated water that is recycled for use in toilet flushing, irrigation and cooling systems. Also known as reuse or reclamation.
Length of time between putting infrastructure in the ground and when the company may seek recovery on the cost.
Treated water that is recycled for use in toilet flushing, irrigation, and cooling systems. Also known as reclamation or reclaimed water.
The water that is analyzed for the presence of EPA-regulated drinking water contaminants. Depending on the regulation, EPA requires water systems and states to take samples from source water, from water leaving the treatment facility, or from the taps of selected consumers.
An on-site review of the water sources, facilities, equipment, operation, and maintenance of a public water systems for the purpose of evaluating the adequacy of the facilities for producing and distributing safe drinking water.
Secondary Drinking Water Standards
Non-enforceable federal guidelines regarding cosmetic effects (such as tooth or skin discoloration) or aesthetic effects (such as taste, odor, or color) of drinking water.
Sole Source Aquifer
An aquifer that supplies 50 percent or more of the drinking water of an area.
Water in its natural state, prior to any treatment for drinking.
The water that systems pump and treat from sources open to the atmosphere, such as rivers, lakes, and reservoirs.
Transient, Non-Community Water System
A water system which provides water in a place such as a gas station or campground where people do not remain for long periods of time. These systems do not have to test or treat their water for contaminants which pose long-term health risks because fewer than 25 people drink the water over a long period. They still must test their water for microbes and several chemicals.
A required process intended to reduce the level of a contaminant in drinking water.
The cloudy appearance of water caused by the presence of tiny particles. High levels of turbidity may interfere with proper water treatment and monitoring.
Ultraviolet Disinfection System
System that eliminates bacteria in water using ultraviolet radiation.
Finding alternatives for designs, materials, processes and systems without diminishing quality or customer satisfaction.
State or EPA permission not to meet a certain drinking water standard. The water system must prove that: (1) it cannot meet a MCL, even while using the best available treatment method, because of the characteristics of the raw water, and (2) the variance will not create an unreasonable risk to public health. The State or EPA must review, and allow public comment on, a variance every three years. States can also grant variances to water systems that serve small populations and which prove that they are unable to afford the required treatment, an alternative water source, or otherwise comply with the standard.
A failure to meet any state or federal drinking water regulation.
Water Line Protection
Service offering to customers that protects them against the cost of repairing broken or leaking pipes.
The land area from which water drains into a stream, river, or reservoir.
Wellhead Protection Area
The area surrounding a drinking water well or well field which is protected to prevent contamination of the well(s).
A wastewater treatment plant that recycles 100 percent of the treated water, rather than discharging some into the local waterways.
Glossary courtesy of the United States Environmental Protection Agency [epa.gov/safewater/glossary.htm]