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The federal Safe Drinking Water Act governs the quality and testing of all public drinking water supplied by water systems in the United States. The EPA works with states, localities and water suppliers to implement drinking water regulations.
Drinking water supplied by public water systems (PWS) in Delaware is regulated by the DHSS Division of Public Health to ensure compliance with the National Primary Drinking Water Regulations.
The National Primary Drinking Water Regulations are legally enforceable standards and treatment techniques that include maximum contaminant levels (MCLs) for regulated contaminants.
Researchers have continued to develop new and more effective methods to understand the possible health effects of PFAS. Delaware has adopted and will maintain the highest standards for public drinking water, based on reasonable scientific review and focused on protecting public health.
In April 2024, the EPA adopted Maximum Contaminant Levels (MCLs) for five PFAS compounds in public drinking water systems (PWS). The levels are expressed in parts per trillion (ppt):
A Hazard Index (HI) of 1 has also been established for any sample containing a mixture of two or more of the PFAS compounds PFNA, PFHxS, HFPO-DA and PFBS (perfluorobutane sulfonic acid). PFBS is only included in the Hazard Index calculation. At a Hazard Index of 1, or higher, the combined levels of chemicals pose potential health concerns and require action.
The details and timeframe of the EPA’s adoption of regulatory standards for PFAS in public drinking water are included in the Delaware PFAS Action Plan from the DHSS Office of Drinking Water.
On May 18, 2026, the EPA announced two proposed rules related to PFAS in drinking water.
One proposed rule would allow public drinking water systems to request two additional years, to 2031, to comply with enforceable limits.
Another proposed rule rolls back federal Safe Drinking Water Act (SDWA) requirements and rescinds drinking water regulations for PFHxS, PFNA, HFPO-DA (commonly known as GenX), and the Hazard Index mixture of these three PFAS compounds, plus PFBS.
The DHSS Office of Drinking Water has proposed adopting EPA’s April 2024 National Primary Drinking Water Regulation for PFAS, by reference, by amending Delaware’s public drinking water regulations.
Separately, an update to Delaware State Law in 2025, the Delaware Forever Chemicals Mandatory Reporting Act, established public notification and reporting requirements when PFAS concentrations exceed the levels specified in the Act.
As of 2026, public drinking water systems must start direct notification to the public of any PFAS monitoring or testing that finds exceeding values.
Starting in 2029, public drinking water systems will have to comply with all MCLs and notify the public of all PFAS MCL violations.
Public drinking water systems that need assistance attaining the PFAS maximum contaminant levels can find information on options and potential financial assistance from the Delaware Department of Health and Social Services (DHSS) Delaware Drinking Water State Revolving Fund (DWSRF).
The Environmental Finance Center Network (EFCN), a university- and non-profit-based organization, provides guidance on applying for DWSRF funding and accessing technical assistance.
DNREC and partners conducted statewide groundwater sampling through existing public potable wells based on a sampling plan that details the dynamic sampling approach and protocols used to conduct the survey.
The result of that sampling is a Persistent Pollutants Sampling Report that details the actions taken, significant detections and overall distribution of select PFAS compounds across Delaware.
DNREC, in partnership with the EPA, is conducting an evaluation of PFAS discovered during statewide groundwater sampling within the coastal plain of Delaware.
The study is collecting data in a variety of environmental media at specific locations. The data and information will be used to prioritize more detailed investigations and to identify potential sources of PFAS affecting water resources.
A Field Sampling Plan, developed with EPA concurrence, details the collection of samples in soil, groundwater, private wells, surface water and sediment.
This study is a follow-up to the Persistent Pollutants Sampling Report.
An estimated 20 percent of Delawareans get their household drinking water from private drinking water wells. Groundwater (water stored in aquifers below the surface of the earth), directly supplies all private wells. Delaware state agencies have made it a priority that private drinking water wells are afforded the same level of protection as public drinking water systems.
Unlike public drinking water systems, private wells are not regulated under the federal Safe Drinking Water Act. Homeowners are responsible for maintaining and testing their own wells.
DNREC and DHSS encourage private well owners to test their private wells every 12 to 14 months for standard drinking water parameters to better understand the quality of their drinking water. To help private well owners with this task, DNREC and DHSS offer free sampling of private drinking water wells, including for per and polyflouroalkyl substances (PFAS), through the Private Drinking Water Well Sampling program (below).
If PFAS or other standard parameters are detected in private drinking water at concentrations above the PFAS Maximum Contaminant Level (MCL) established by the EPA and in the Delaware Forever Chemicals Mandatory Reporting Act, DNREC and DHSS implement a response plan, which may include short term mitigation, monitoring and studies to determine alternate sources of water and/or water treatment, to ensure that water supplies are safe to consume.
Learn more about private wells, ground water and drinking water from the EPA.
Find information about private well classes and other water well owner resources.
The Department of Natural Resources and Environmental Control (DNREC), in partnership with the Department of Health and Social Services (DHSS), is sampling private drinking water wells in Delaware to test for a list of possible contaminants to help protect public health and the environment.
The contaminants to be tested for include per- and polyfluoroalkyl substances (PFAS), nitrate, nitrite, iron, fluoride, alkalinity, pH, chloride, sulfate, sodium, hardness, Escherichia coli (E. coli) and total coliform.
If you would like your private well to be sampled, please complete the Private Well Water Sampling Request and Consent Form.
This service is provided free of charge.
Water contaminated with PFAS can be treated with carbon filters and reverse osmosis. The American National Standards Institute (ANSI) publishes standards (NSF/ANSI 53 and 58) related to the removal of PFAS through these systems.
The National Sanitation Foundation lists products it has certified to reduce PFOA/PFOS in drinking water.
Related Topics: drinking water, EPA, GenX, PFAS, PFOA, waste and hazardous substances, watar, water, wells
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