What testing found in Merrimack's water

The Merrimack Village District's public water system now meets all federal limits for PFAS contamination, according to the most recent EPA testing data. The system, which serves all 25,500 residents of Merrimack, showed no detectable levels of any PFAS compounds above federal maximum contaminant levels in samples collected between 2023 and 2026 under the EPA's Unregulated Contaminant Monitoring Rule 5 program.

This result represents a major turnaround for a community that became a national symbol of PFAS contamination less than a decade ago. The clean test results reflect years of treatment system installation and millions of dollars in infrastructure investment, much of it paid for by the company responsible for the contamination.

The EPA finalized these federal limits in April 2024 after determining there is no safe level of exposure to PFOA and PFOS, two of the most studied PFAS compounds. The limits are 4 parts per trillion for PFOA, 4 ppt for PFOS, 10 ppt for PFHxS, 10 ppt for PFNA, and 10 ppt for GenX.

What this means for Merrimack residents

The current test results show that Merrimack's treated public water supply is safe to drink under federal standards. Residents connected to the Merrimack Village District system can use tap water for drinking, cooking, and preparing infant formula without additional filtration for PFAS.

This was not always the case. Before treatment systems were installed, PFAS contamination in Merrimack's groundwater posed serious health risks. According to the EPA, long-term exposure to PFOA has been linked to kidney cancer, testicular cancer, liver damage, thyroid disease, high cholesterol, ulcerative colitis, pregnancy-induced hypertension, and reduced immune response to vaccines. PFOS carries similar risks, including impacts on liver function, immune system development in children, and cholesterol levels.

Pregnant women, infants, and people with compromised immune systems face the highest risk from PFAS exposure. The primary exposure routes are drinking contaminated water and using it for cooking. Bathing and showering in water containing PFAS poses minimal risk because these chemicals are not readily absorbed through skin.

The health concern in Merrimack now centers on residents still using private wells that may remain contaminated, and on the long-term effects of past exposure for people who drank contaminated water before treatment systems were installed.

Where these chemicals came from

PFAS contamination in Merrimack came from the Saint-Gobain Performance Plastics facility, which operated in the town for decades manufacturing products that used PFAS compounds. The state of New Hampshire identified the plant as the source of contamination that spread through air emissions and groundwater across Merrimack and four neighboring communities: Litchfield, Bedford, Hudson, and Londonderry.

The contamination became public in 2016 when testing discovered PFAS in hundreds of private and public wells around the facility. New Hampshire Public Radio reported that the discovery launched years of legal battles, community organizing, and cleanup efforts.

In 2019, Merrimack voters approved a $14.5 million bond for the Merrimack Village District to install treatment systems on four contaminated public wells, according to New Hampshire Bulletin. Saint-Gobain agreed to pay for treatment on two additional wells.

Under a 2022 consent decree, Saint-Gobain agreed to provide clean drinking water to about 1,000 homes whose private wells were contaminated. In March 2026, InDepthNH.org reported that the New Hampshire Attorney General announced a deal extending Saint-Gobain's obligation to connect 350 additional properties to public water.

Saint-Gobain ended operations at the Merrimack plant in May 2024 and completed demolition of the facility in 2025, according to New Hampshire Public Radio.

What Merrimack is doing about it

The Merrimack Village District installed granular activated carbon treatment systems on its contaminated wells starting in 2019. These systems filter PFAS compounds out of groundwater before it enters the distribution system. The EPA's most recent testing confirms that this treatment is working, with finished water meeting all federal standards.

The district continues to monitor water quality and maintain its treatment systems. Water utilities across the country must begin compliance monitoring for PFAS by 2027, with full compliance required by 2029, but Merrimack's systems are already meeting these future requirements.

Beyond the public water system, Saint-Gobain's obligation to connect private well users to public water continues. The company has connected about 1,000 homes so far, with 350 more connections planned under the 2026 agreement with the state.

The cleanup is not finished. Merrimack Citizens for Clean Water and other community groups continue to push for full remediation of contaminated soil at the former plant site. New Hampshire Bulletin reported that town leaders are seeking a fair share of national PFAS settlement funds to cover ongoing costs.

Steps Merrimack residents can take today

Residents connected to the Merrimack Village District can take these actions:

  • Request your water system's Consumer Confidence Report, which utilities must provide annually. Contact the Merrimack Village District or search online for "Merrimack Village District consumer confidence report."

  • If you use a private well, get it tested for PFAS. The New Hampshire Department of Environmental Services can provide information on certified labs.

  • Even though public water now meets federal standards, you can install additional home filtration for peace of mind. Look for filters certified to NSF/ANSI Standard 53 for PFAS reduction (pitcher or under-sink activated carbon filters) or NSF/ANSI Standard 58 (reverse osmosis systems). Check that the specific filter model lists PFAS or PFOA/PFOS reduction in its certification.

  • Attend Merrimack Village District meetings and town council meetings to stay informed about water quality issues and remediation progress.

  • Learn more about PFAS contamination and what you can do at CheckYourWater's action page.

  • Review the full testing data for the Merrimack Village District at the system data page.

Full test results

Complete testing data for the Merrimack Village District is available on the system page. The data comes from the EPA's Unregulated Contaminant Monitoring Rule 5 program, with samples collected between 2023 and 2026. UCMR 5 tests measure PFAS levels at the entry point to the distribution system, after treatment but before water reaches individual homes. The testing does not reflect any additional filtration that households may use.