Private Well Water Metadata: Homes on Well Water and Testing Behavior


Adults with homes on well water and water testing behavior data are from the Behavioral Risk Factor Surveillance System (BRFSS).

Dates Available:

Single years 2012, 2014-2019, 2021; combined years 2016-2019 and 2021

Geographic Resolution:

State, Public Health District, County


This data set contains information on the percent of adults with homes using private well water in Maine; the percent of adults with private well water that have tested their water; and the percent of adults with private well water that have tested their well water for arsenic. Data are stratified by geographic location housing type (i.e. own, rent), income, and education level. 

The dataset contains the following measures:

  1. Percentage of adults with private well water
  2. Percentage of adults with any water test among homes with private well water
  3. Percentage of adults with an arsenic water test among homes with private well water


This data set supports efforts to improve public health in Maine and contributes to the U.S. CDC’s National Environmental Public Health Tracking (EPHT) Network. A key activity of participants in this network is to track and make available environmental health measures on state and national portals. Measures derived from the data set described here can be used to compare private well water testing behavior across the state, over time, and in relation to risk factors and laboratory test results.

The Maine Tracking Network (ME Tracking), a member of the National EPHT Network, connects communities, public health professionals, policy makers, state agencies, and others to the data they need to monitor public health, respond to health concerns, prioritize resources for public health action, and evaluate prevention activities. Maine tracks certain health effects, exposures, and environmental hazards that have known relationships, as well as some health effects and environmental hazards that have suspected relationships.  By making health and environmental data available through the Maine Tracking Network, more people have access to data they need to think critically and hypothesize about health outcomes and their relationships to conditions in the environment.

Supplemental Information:

More than half of the homes in Maine get drinking water from private, residential wells.  Many Maine wells have too much  arsenic or other contaminants of concern.  Private well users are responsible for testing their water and treating any hazards.

The BRFSS is conducted nationally in 50 states, the District of Columbia, Puerto Rico, the U.S. Virgin Islands, and Guam. In Maine, more than 4,000 adults are interviewed each year. Private well water testing behavior questions were first included in the survey in 2003 and then every 2 or 3 three years beginning in 2009.

Statistical weighting is an analytical technique used to account for survey non-response, in addition to known distributions of age, race and ethnicity, gender, geographic region and other characteristics of populations.  From 1984 to 2010, the BRFSS used a technique called post-stratification to weight BRFSS survey data. In 2011, a new statistical method called raking replaced the older method because it could help record additional population characteristics such as education level, marital status, and home ownership status of respondents. Household weighting was modified again in 2015 to include cell phone respondents. Changes in the estimated percentage of BRFSS measures from year to year could be due to changes in survey methodology.

Entity and Attribute Overview:

This dataset includes the following fields: weighted count (with accompanying 95% CI's), weighted percent (with accompanying 95% CI’s) of homes with private well water, weighted percent (with accompanying 95% CI’s) of homes with any water test among homes with private well water, weighted percent (with accompanying 95% CI’s) of home with an arsenic test among homes with private well water, survey year, geographic resolution, and household status (own, rent).

Data Limitations:

  • Maine adults who are institutionalized, do not have a phone, or cannot communicate over the phone are not interviewed by the survey.
  • Data are based upon self-report, and individuals may or may not be able to report accurately that their household well water has been tested or whether their well water has been tested specifically for the presence of arsenic.
  • While the prevalence data are statistically weighted to be more representative of the general adult population of Maine and to adjust for non-response, statistical weighting methods are not always perfect in accomplishing this.
  • In general, only a small percentage (less than 10%) of people who respond to these survey questions answer “I don’t know” to any given question. However, when survey participants were asked whether they had tested their well for arsenic, a relatively high percentage (>10% statewide) answered that they did not know. This is not surprising; arsenic can be included in a basic water test, without being specifically requested. The implication is that the percent of homes tested for arsenic may be higher than results from the survey, since estimates reflect only those who reported being certain that they had tested.

Access Constraints:

Publicly available data are suppressed in accordance with the Maine CDC Privacy Policy to protect confidentiality.

More Information:

Suggested Citation for Data Displays:

Maine Center for Disease Control and Prevention, Maine Tracking Network.  Private Well Water Metadata: Homes with Private Well Water and Testing Behavior. Available online: Accessed on [date accessed].