Public Water Supply

Types of Public Water Systems

There are three categories of regulated water systems: community, non-transient non-community, and transient non-community. Data are available here for community and non-transient non-community systems. The different categories determine water testing and compliance requirements. Use the map to explore locations of systems and populations served.

Per- and Polyfluoroalkyl Substances (PFAS)

PFAS refers to a family of chemicals known as per- and polyfluoroalkyl substances. PFAS have been used for a long time in many household and industrial products. In 2021, the Maine legislature mandated that all community public water systems and non-transient, non-community schools and daycares sample their drinking water for PFAS. The Maine legislature also established a State drinking water standard of 20 parts per trillion (ppt) for the combined sum of six PFAS (PFOA, PFOS, PFHpA, PFNA, PFDA, PFHxS). A National Primary Drinking Water Regulation established a Maximum Contaminant Level of 4 ppt for PFOA and PFOS.

Lead in School Water

Lead is a heavy metal that can enter drinking water through plumbing. Before 1987, solder that contained lead was commonly used to join copper pipes. In 2019, the Maine legislature mandated all K-12 schools in Maine test their drinking water for lead. It is recommended that schools stop using all fixtures with lead levels at or above 4 parts per billion (ppb). We show only initial results and summaries in the map and table view. Click a school dot on the map to see detailed results to the right.

Historical Testing Results

All public water systems are required to regularly sample and test their water to ensure it meets federal and state drinking water standards. Maine CDC’s Drinking Water Program sets the frequency for testing certain contaminants, or analytes. Not all contaminants are required to be tested every year and may show up as No Sample on a recurring basis. These displays present maps and trend charts for selected contaminants found in community water systems (CWS) from 1999-2023.

Test Result Tables

Create and download custom tables of analyte results.

General Information and Measure Definitions

• Mapped Locations
  • The locations mapped do not represent water source locations such as wells, surface reservoirs, or treatment operation plants. 
  • Types of Public Water Systems, PFAS Results, and Selected Contaminants: We assign point locations to community and non-transient non-community supplies in order to approximate where water is being provided.
  • Municipal systems: We assign point locations to the centroid of the principal town being served. For residential developments as well as schools or other institutions having their own regulated supply, we assign a representative address such as that of a central building.
  • For lead in water testing results in schools, point locations are derived from school addresses. 

• PFAS Testing
  • The Maine legislature mandated that all community public water systems and non-transient, non-community (NTNC) schools and daycares sample their finished drinking water for PFAS. Initial monitoring had a deadline of December 31, 2022. Subsequent monitoring occurred for systems with detectable levels of PFAS and is ongoing.  
  • The Maine legislation established an interim Maine standard of 20 ppt (parts per trillion) for six PFAS compounds (alone or in combination). A National Primary Drinking Water Regulation (NPDWR) for six PFAS was announced by the EPA on April 2024, which established a set of Maximum Contaminant Levels, including limits of 4 ppt for individual types of PFAS known as PFOA and PFOS. We color code map displays using 20 ppt as a threshold for the "sum of 6" PFAS, and 4 ppt as a threshold for PFOA and PFOS. The "Sum of 6" measure is a combined value for six different PFAS: PFOA, PFOS, PFHpA, PFNA, PFDA, PFHxS. 
  • As both testing and mitigation efforts are ongoing, the map display allows display of either the most recent result for each water system, or the initial result. For systems sampling from multiple facilities at once (i.e. multiple treatment points), we display the maximum value obtained. We display detailed sample results by specific dates in the Tables tab. Blank cells in the Tables view indicate missing values: for example, Sum of 6 results may not be available for the latest sampling date, though PFOA or PFOS results are reported.  
• Lead in School Water Testing Results
  • The Maine Legislature mandated that all K-12 schools in Maine test their drinking water for the presence of lead. The sampling program ended June 30, 2023.
  • Because lead contamination comes primarily from fixtures (faucets, water coolers) and plumbing, each school took standing water (first draw) samples from wherever school occupants might obtain water.
  • We show initial results and summaries in the data displays. Maps present average lead levels for each school. The tables view shows individual fixture results. To access post-remediation results, contact the individual schools.  

• Selected Contaminants
  • MaineTracking produces community water system measures related to a select group of routinely monitored contaminants. We select these contaminants in coordination with national and state Tracking programs because they occur more frequently in drinking water at levels that may be of public health significance.  
  • We display average and maximum levels for the year. For sample results below detection, we substitute a value of 1/2 the detection limit. Tables tab shows the number of samples below detection. In maps, we color coded systems by summary value above or below the regulated MCL (maximum contaminant level) concentration.  
  • Data represent "community" type water supplies, with an active status prior to December 31 of the reporting year. 
  • We calculate percent of systems, and percent of population, as the percent among those systems with test results for the given contaminant in the reporting year. Community water systems do not test every analyte every year. Systems with "no sample" for the year are shown as such on the map, and this does not generally indicate a reporting violation. 

Data Limitations

• Mapped Locations
  • Precise service area boundaries for water supplies are not currently available for all systems represented. Point locations are intended to represent the general location where water is provided.

• PFAS Testing
  • These data cannot tell us the precise concentration of PFAS delivered to household or institutional taps at any particular time.
  • Data provided here may not be the latest available. Footer text will give the month/year of latest update.
  • These data are recent and may not represent historical levels of contamination. 
• Lead Testing in Schools
  • Only initial results from the testing program are shown.
  • Results were obtained from standing water (first draw) testing, Usually, the amount of lead in water is highest on first draw tests. After water runs for a minute or longer the level reduces. That is why this test is used to find out if lead is dissolving into the water rather than how much lead someone is being exposed to.  
• Selected Contaminants
  • These data cannot tell us the precise concentration of contaminants delivered to households. 
  • Sampling frequency varies by system and contaminant, such that not every contaminant is sampled every year.