Domestic (Private) Supply Wells Active
What’s in Your Well Water?
USGS studies the quality of this key source of drinking water and potential concerns for domestic well users
More than 43 million people—about 15 percent of the U.S. population—rely on domestic (private) wells as their source of drinking water. The quality and safety of water from domestic wells are not regulated by the Federal Safe Drinking Water Act or, in most cases, by state laws. Instead, individual homeowners are responsible for maintaining their domestic well systems and for monitoring water quality.
Featured: 3-D Models of As and Mn in the Glacial Aquifer System
New 3-D models from the USGS National Water Quality Program predict where high concentrations of arsenic and manganese likely occur in the glacial aquifer system, groundwater supply for 30 million. Redox conditions and pH are controlling factors.
The USGS National Water Quality Program investigates the quality of water pumped from domestic wells across the United States. These wells are the sole source of drinking water and water for other household needs for most people in many rural areas. Health risks associated with contaminants in domestic well water include gastrointestinal illness related to bacteria and other pathogens and exposure to elevated concentrations of nitrate, arsenic, radon, lead, and organic compounds. Typically, the water supplied by domestic wells is not routinely tested. As a result, people using domestic-supply wells could be drinking water with elevated concentrations of some contaminants.
The quality and safety of water from privately owned domestic wells is not regulated under Federal or, in most cases, state laws. Homeowners are primarily responsible for maintaining their domestic well systems and for any water-quality monitoring. Federal regulations under the Safe Drinking Water Act (SDWA) for public water supplies, although not directly applicable to the regulation of domestic wells, provide useful concentration benchmarks for evaluating the quality of water from domestic wells in a human-health context.
Water Quality of Domestic Wells
In a study of 2,100 domestic wells, water pumped from about one in five wells contained one or more contaminants at a concentration greater than a human-health benchmark for drinking water. Supporting information and summary data for the study can be found here.
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The contaminants most often found at these elevated concentrations were inorganic chemicals, such as metals, radionuclides, and nitrate; all of these but nitrate are derived primarily from natural sources.
-
Man-made organic compounds, such as pesticides and solvents, were detected in more than half (60 percent) of the domestic wells sampled, but concentrations were seldom greater than human-health benchmarks (less than 1 percent of wells).
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About half of the wells had at least one “nuisance” contaminant—a compound that impairs taste, odor, or other aesthetic considerations—at a level or concentration outside the range of values recommended by the U.S. Environmental Protection Agency.
-
Microbial contaminants (for example, bacteria) were detected in about one-third of the approximately 400 wells that had their water analyzed for those contaminants.
-
Contaminants found in domestic wells usually co-occurred with other contaminants as mixtures, rather than alone, which is a potential concern because the total toxicity of a mixture can be greater than that of any single contaminant.
More information on the quality of water from domestic wells is provided in USGS publications that summarize the quality of water in Principal Aquifers in nine regions of the United States and specifically groundwater tapped by domestic wells in Principal Aquifers.
Where Are Domestic Wells Used?
USGS maps show where people across the Nation rely on private wells for their drinking water. The maps estimate the number of people using private wells in a given area, but individual wells are not identified. The maps can help determine where focused groundwater-quality testing or further studies are needed to help ensure safe drinking water from private wells. For instance, overlaying information on private well use with a map of potentially corrosive groundwater could be used to focus water-quality testing for lead in areas with a high density of private wells and a high likelihood of potentially corrosive groundwater.
Types of Domestic Wells
There are several types of domestic wells used by homeowners. The oldest wells were dug by hand. These wells typically are shallow and of large diameter (several feet), and may be lined with stones, brick, or tile. They typically extend only a short distance below the water table. Driven wells are constructed by driving small-diameter pipe into saturated unconsolidated sand and gravel. Driven wells typically are deeper than dug wells but are still relatively shallow. Most modern wells are drilled using truck-mounted machines and rotary or percussion methods. Drilled wells may be several hundred to more than a thousand feet deep, and can penetrate consolidated sediment and bedrock. Drilled wells in unconsolidated sediment have a well casing and a well screen to prevent collapse of the surrounding rock and sediment into the well. Drilled wells in bedrock typically are cased through the overlying soil and thin sediment and are open holes below. Domestic wells typically pump water from shallower depths than public-supply wells.
Interested in the water quality of public-supply wells?
Information on USGS studies of the deep wells that supply the water used by most of us for drinking can be found here.
Explore these topics related to groundwater quality
- Arsenic
- Chloride and salinity
- Corrosivity
- Groundwater age dating
- Hydraulic fracturing
- Metals
- Nutrients
- Pesticides
- Radionuclides
- Oxidation/reduction (redox)
- Surface-water/groundwater interaction
- Volatile organic compounds
Follow the links below to web pages that describe USGS science on these groundwater-quality topics.
Public Supply Wells
Follow the links below to access data and tools on water quality of domestic supply wells.
Find links below to multimedia associated with domestic wells.
Learn about USGS research on the water quality of domestic wells and other groundwater quality issues at the publications listed below.
Estimating the high-arsenic domestic-well population in the conterminous United States
The quality of our Nation's waters: Water quality in principal aquifers of the United States, 1991-2010
Modeling nitrate at domestic and public-supply well depths in the Central Valley, California
The quality of our Nation's waters: Water quality in the Denver Basin aquifer system, Colorado, 2003-05
Assessment of arsenic concentrations in domestic well water, by town, in Maine 2005-09
Estimates for self-supplied domestic withdrawals and population served for selected principal aquifers, calendar year 2005
The quality of our Nation’s waters: Quality of water from public-supply wells in the United States, 1993–2007: Overview of major findings
Factors Affecting Water Quality in Domestic Wells in the Upper Floridan Aquifer, Southeastern United States, 1998-2005
Water Quality in the High Plains Aquifer, Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming, 1999-2004
Quality of Water from Domestic Wells in Principal Aquifers of the United States, 1991-2004
The quality of our nation’s waters: Quality of water from domestic wells in principal aquifers of the United States, 1991–2004— Overview of major findings
Quality of ground water from private domestic wells
Summary of selected U.S. Geological survey data on domestic well water quality for the Centers for Disease Control's National Environmental Public Health Tracking Program
Follow the links below to access data and tools on water quality of domestic supply wells.
Below are news stories associated with this project.
- Overview
More than 43 million people—about 15 percent of the U.S. population—rely on domestic (private) wells as their source of drinking water. The quality and safety of water from domestic wells are not regulated by the Federal Safe Drinking Water Act or, in most cases, by state laws. Instead, individual homeowners are responsible for maintaining their domestic well systems and for monitoring water quality.
Featured: 3-D Models of As and Mn in the Glacial Aquifer SystemNew 3-D models from the USGS National Water Quality Program predict where high concentrations of arsenic and manganese likely occur in the glacial aquifer system, groundwater supply for 30 million. Redox conditions and pH are controlling factors.
The USGS National Water Quality Program investigates the quality of water pumped from domestic wells across the United States. These wells are the sole source of drinking water and water for other household needs for most people in many rural areas. Health risks associated with contaminants in domestic well water include gastrointestinal illness related to bacteria and other pathogens and exposure to elevated concentrations of nitrate, arsenic, radon, lead, and organic compounds. Typically, the water supplied by domestic wells is not routinely tested. As a result, people using domestic-supply wells could be drinking water with elevated concentrations of some contaminants.
The quality and safety of water from privately owned domestic wells is not regulated under Federal or, in most cases, state laws. Homeowners are primarily responsible for maintaining their domestic well systems and for any water-quality monitoring. Federal regulations under the Safe Drinking Water Act (SDWA) for public water supplies, although not directly applicable to the regulation of domestic wells, provide useful concentration benchmarks for evaluating the quality of water from domestic wells in a human-health context.
Water Quality of Domestic Wells
In a study of 2,100 domestic wells, water pumped from about one in five wells contained one or more contaminants at a concentration greater than a human-health benchmark for drinking water. Supporting information and summary data for the study can be found here.
-
The contaminants most often found at these elevated concentrations were inorganic chemicals, such as metals, radionuclides, and nitrate; all of these but nitrate are derived primarily from natural sources.
-
Man-made organic compounds, such as pesticides and solvents, were detected in more than half (60 percent) of the domestic wells sampled, but concentrations were seldom greater than human-health benchmarks (less than 1 percent of wells).
-
About half of the wells had at least one “nuisance” contaminant—a compound that impairs taste, odor, or other aesthetic considerations—at a level or concentration outside the range of values recommended by the U.S. Environmental Protection Agency.
-
Microbial contaminants (for example, bacteria) were detected in about one-third of the approximately 400 wells that had their water analyzed for those contaminants.
-
Contaminants found in domestic wells usually co-occurred with other contaminants as mixtures, rather than alone, which is a potential concern because the total toxicity of a mixture can be greater than that of any single contaminant.
More information on the quality of water from domestic wells is provided in USGS publications that summarize the quality of water in Principal Aquifers in nine regions of the United States and specifically groundwater tapped by domestic wells in Principal Aquifers.
Where Are Domestic Wells Used?
USGS maps show where people across the Nation rely on private wells for their drinking water. The maps estimate the number of people using private wells in a given area, but individual wells are not identified. The maps can help determine where focused groundwater-quality testing or further studies are needed to help ensure safe drinking water from private wells. For instance, overlaying information on private well use with a map of potentially corrosive groundwater could be used to focus water-quality testing for lead in areas with a high density of private wells and a high likelihood of potentially corrosive groundwater.
Types of Domestic Wells
There are several types of domestic wells used by homeowners. The oldest wells were dug by hand. These wells typically are shallow and of large diameter (several feet), and may be lined with stones, brick, or tile. They typically extend only a short distance below the water table. Driven wells are constructed by driving small-diameter pipe into saturated unconsolidated sand and gravel. Driven wells typically are deeper than dug wells but are still relatively shallow. Most modern wells are drilled using truck-mounted machines and rotary or percussion methods. Drilled wells may be several hundred to more than a thousand feet deep, and can penetrate consolidated sediment and bedrock. Drilled wells in unconsolidated sediment have a well casing and a well screen to prevent collapse of the surrounding rock and sediment into the well. Drilled wells in bedrock typically are cased through the overlying soil and thin sediment and are open holes below. Domestic wells typically pump water from shallower depths than public-supply wells.
Interested in the water quality of public-supply wells?
Information on USGS studies of the deep wells that supply the water used by most of us for drinking can be found here.
Explore these topics related to groundwater quality
- Arsenic
- Chloride and salinity
- Corrosivity
- Groundwater age dating
- Hydraulic fracturing
- Metals
- Nutrients
- Pesticides
- Radionuclides
- Oxidation/reduction (redox)
- Surface-water/groundwater interaction
- Volatile organic compounds
-
- Science
Follow the links below to web pages that describe USGS science on these groundwater-quality topics.
Public Supply Wells
Are you among the more than 100 million people in the U.S. who relies on a public-supply well for your drinking water? Although the quality of finished drinking water from public water systems is regulated by the EPA, long-term protection and management of the raw groundwater tapped by public-supply wells requires an understanding of the occurrence of contaminants in this invisible, vital resource... - Data
Follow the links below to access data and tools on water quality of domestic supply wells.
- Multimedia
Find links below to multimedia associated with domestic wells.
- Publications
Learn about USGS research on the water quality of domestic wells and other groundwater quality issues at the publications listed below.
Estimating the high-arsenic domestic-well population in the conterminous United States
Arsenic concentrations from 20 450 domestic wells in the U.S. were used to develop a logistic regression model of the probability of having arsenic >10 μg/L (“high arsenic”), which is presented at the county, state, and national scales. Variables representing geologic sources, geochemical, hydrologic, and physical features were among the significant predictors of high arsenic. For U.S. Census blocAuthorsJoseph D. Ayotte, Laura Medalie, Sharon L. Qi, Lorraine C. Backer, Bernard T. NolanFilter Total Items: 29The quality of our Nation's waters: Water quality in principal aquifers of the United States, 1991-2010
About 130 million people in the United States rely on groundwater for drinking water, and the need for high-quality drinking-water supplies becomes more urgent as our population grows. Although groundwater is a safe, reliable source of drinking water for millions of people nationwide, high concentrations of some chemical constituents can pose potential human-health concerns. Some of these contaminAuthorsLeslie A. DeSimone, Peter B. McMahon, Michael R. RosenModeling nitrate at domestic and public-supply well depths in the Central Valley, California
Aquifer vulnerability models were developed to map groundwater nitrate concentration at domestic and public-supply well depths in the Central Valley, California. We compared three modeling methods for ability to predict nitrate concentration >4 mg/L: logistic regression (LR), random forest classification (RFC), and random forest regression (RFR). All three models indicated processes of nitrogen feAuthorsBernard T. Nolan, JoAnn M. Gronberg, Claudia C. Faunt, Sandra M. Eberts, Ken BelitzThe quality of our Nation's waters: Water quality in the Denver Basin aquifer system, Colorado, 2003-05
Availability and sustainability of groundwater in the Denver Basin aquifer system depend on water quantity and water quality. The Denver Basin aquifer system underlies about 7,000 square miles of the Great Plains in eastern Colorado and is the primary or sole source of water for domestic and public supply in many areas of the basin. Use of groundwater from the Denver Basin sandstone aquifers has bAuthorsNancy J. Bauch, MaryLynn Musgrove, Barbara Mahler, Suzanne PaschkeAssessment of arsenic concentrations in domestic well water, by town, in Maine 2005-09
Prior studies have established that approximately 10 percent of domestic wells in Maine have arsenic levels greater than the U.S. Environmental Protection Agency maximum contaminant limit (10 micrograms per liter (ug/L)). Of even greater concern are multiple discoveries of wells with very high arsenic levels (> 500 ug/L) in several areas of the State. A study was initiated to assist the Maine CentAuthorsM.G. Nielsen, P.J. Lombard, L.F. SchalkEstimates for self-supplied domestic withdrawals and population served for selected principal aquifers, calendar year 2005
The National Water-Quality Assessment Program of the U.S. Geological Survey has groundwater studies that focus on water-quality conditions in principal aquifers of the United States. The Program specifically focuses on aquifers that are important to public supply, domestic, and other major uses. Estimates for self-supplied domestic withdrawals and the population served for 20 aquifers in the UniteAuthorsMolly A. Maupin, Terri ArnoldThe quality of our Nation’s waters: Quality of water from public-supply wells in the United States, 1993–2007: Overview of major findings
Summary of Major Findings and Implications About 105 million people in the United States-more than one-third of the Nation's population-receive their drinking water from about 140,000 public water systems that use groundwater as their source. Although the quality of finished drinking water (after treatment and before distribution) from these public water systems is regulated by the U.S. EnvironmeAuthorsPatricia L. Toccalino, Jessica A. HoppleFactors Affecting Water Quality in Domestic Wells in the Upper Floridan Aquifer, Southeastern United States, 1998-2005
The Floridan aquifer system is a highly productive carbonate aquifer that provides drinking water to about 10 million people in Florida, Georgia, and South Carolina. Approximately 1.6 million people rely on domestic wells (privately owned household wells) for drinking water. Withdrawals of water from the Floridan aquifer system have increased by more than 500 percent from 630 million gallons per dAuthorsMarian P. Berndt, Christy A. Crandall, Michael Deacon, Teresa L. Embry, Rhonda S. HowardWater Quality in the High Plains Aquifer, Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming, 1999-2004
This report contains the major findings of a 1999-2004 assessment of water quality in the High Plains aquifer. It is one of a series of reports by the National Water-Quality Assessment (NAWQA) Program that present major findings for principal and other aquifers and major river basins across the Nation. In these reports, water quality is discussed in terms of local, regional, State, and national isAuthorsJason J. Gurdak, Peter B. McMahon, Kevin Dennehy, Sharon L. QiQuality of Water from Domestic Wells in Principal Aquifers of the United States, 1991-2004
As part of the National Water-Quality Assessment Program of the U.S. Geological Survey (USGS), water samples were collected during 1991-2004 from domestic wells (private wells used for household drinking water) for analysis of drinking-water contaminants, where contaminants are considered, as defined by the Safe Drinking Water Act, to be all substances in water. Physical properties and the concentAuthorsLeslie A. DeSimoneThe quality of our nation’s waters: Quality of water from domestic wells in principal aquifers of the United States, 1991–2004— Overview of major findings
More than 43 million people - about 15 percent of the U.S. population - rely on domestic wells as their source of drinking water (Hutson and others, 2004). The quality and safety of water from domestic wells, also known as private wells, are not regulated by the Federal Safe Drinking Water Act or, in most cases, by state laws. Rather, individual homeowners are responsible for maintaining their domAuthorsLeslie A. DeSimone, Pixie A. Hamilton, Robert J. GilliomQuality of ground water from private domestic wells
This article highlights major findings from two USGS reports: DeSimone (2009) and DeSimone and others (2009). These reports can be accessed at http://water.usgs.gov/nawqa. This article is followed by a summary of treatment considerations and options for owners of private domestic wells, written by Cliff Treyens of the National Ground Water Association.AuthorsLeslie A. DeSimone, Pixie A. Hamilton, Robert J. GilliomSummary of selected U.S. Geological survey data on domestic well water quality for the Centers for Disease Control's National Environmental Public Health Tracking Program
About 10 to 30 percent of the population in most States uses domestic (private) water supply. In many States, the total number of people served by domestic supplies can be in the millions. The water quality of domestic supplies is inconsistently regulated and generally not well characterized. The U.S. Geological Survey (USGS) has two water-quality data sets in the National Water Information SystemAuthorsRoy C. Bartholomay, Janet M. Carter, Sharon L. Qi, Paul J. Squillace, Gary L. Rowe - Web Tools
Follow the links below to access data and tools on water quality of domestic supply wells.
- News
Below are news stories associated with this project.