Receiving a laboratory report showing PFAS in your private well can be unsettling. Your next question is usually more practical than scientific: what should I do now?

The answer depends on your laboratory results, your household’s water use, and your long-term plans for the property. Before purchasing a filtration system, it’s important to understand what your test results actually mean and how they should guide your next steps.

Key takeaway: A laboratory result is the starting point—not the finish line. Test first, understand the findings, discuss appropriate treatment with a qualified water-treatment professional if needed, and verify performance with follow-up testing after installation.

For Nantucket homeowners, buyers, sellers, and seasonal residents, that approach helps ensure treatment decisions are based on reliable data rather than marketing claims.

Why PFAS Testing Matters for Nantucket Private Wells

PFAS (per- and polyfluoroalkyl substances) are a large group of manufactured chemicals that have been used for decades in products such as stain-resistant fabrics, certain firefighting foams, food packaging, and industrial applications. Because many PFAS break down very slowly, they are sometimes called “forever chemicals.”

Unlike many water-quality issues, PFAS generally cannot be detected by taste, odor, or appearance. A laboratory analysis is the only reliable way to determine whether they are present in drinking water.

The Massachusetts Department of Environmental Protection (MassDEP) recommends that all private drinking-water wells be tested for PFAS, with particular emphasis on wells located within one to two miles of a known PFAS source or another affected water supply.

On Nantucket, PFAS testing also has added importance because private-well property transfers require PFAS testing under current Town requirements — see our guide on well water testing before a Nantucket home sale.

An Important Nantucket Difference: Private Wells Are Not the Same as Municipal Water

One of the most common misconceptions is that municipal water results automatically reflect the quality of nearby private wells.

They do not.

According to the Town of Nantucket, most private residential wells draw water from the island’s upper unconfined aquifer, while several municipal wells obtain water from deeper groundwater separated by a confining layer.

That means:

A municipal-water test does not confirm the quality of an individual private well.
Likewise, conditions affecting one private well do not necessarily represent nearby wells.
Every private well should be evaluated based on its own laboratory results.

This distinction is especially important when buying or selling property or deciding whether treatment is necessary.

Understanding Your PFAS Laboratory Report

If your laboratory detects PFAS, the report may include:

Individual PFAS compounds
A combined PFAS result (depending on the laboratory’s reporting format)
Detection limits
Laboratory reporting limits
Units such as nanograms per liter (ng/L), which are equivalent to parts per trillion (ppt)

The numbers themselves should always be interpreted in the context of current Massachusetts guidance and recommendations.

Rather than comparing your results to information found online or on social media, use current guidance from MassDEP and discuss any questions with qualified professionals who can explain what the results mean for your specific situation.

What Should You Do If PFAS Is Detected?

Finding PFAS in a laboratory report does not automatically mean you need the largest or most expensive filtration system available.

Instead, consider the following steps.

1. Review the Laboratory Report Carefully

Start by confirming:

Which PFAS compounds were detected
The reported concentrations
Whether additional testing may be appropriate
Whether the sample was collected recently

If the sample is older, testing again before making a significant treatment investment may be worthwhile.

2. Consider How Your Household Uses Water

Treatment decisions often depend on factors such as:

Whether the property is occupied year-round or seasonally
Household water demand
Number of occupants
Existing treatment equipment
Future renovation or plumbing plans

A treatment solution that works well for one home may not be appropriate for another.

3. Discuss Treatment with a Qualified Water-Treatment Professional

Treatment professionals can evaluate:

The laboratory findings
Household water usage
Plumbing layout
Equipment sizing
Maintenance requirements

The goal is to match treatment to the specific water-quality issue—not simply install a filter because PFAS was detected.

Choosing a PFAS Filter: What Homeowners Should Know

Many products advertise PFAS removal, but no single filter is appropriate for every situation. Two treatment technologies are commonly used — for a broader look at how these compare to other well-water treatment options, see our guide to the best water filters for private wells on Nantucket.

Activated Carbon

Activated carbon systems—particularly high-quality granular activated carbon (GAC) systems—can reduce many PFAS compounds when properly designed, installed, and maintained.

Depending on the home’s plumbing, activated carbon may be installed as:

A whole-house system
A point-of-use system serving a single tap

Performance depends on several factors, including:

The specific PFAS present
Water chemistry
Water usage
System design
Proper maintenance
Timely media replacement

As the carbon becomes exhausted, treatment performance may decline, making regular maintenance essential.

Reverse Osmosis

Reverse osmosis (RO) systems are another technology commonly used for reducing many PFAS compounds.

Unlike whole-house carbon systems, reverse osmosis is usually installed as a point-of-use treatment system serving drinking and cooking water.

Reverse osmosis systems typically require:

Pre-filters
Membrane replacement
Periodic maintenance
Proper installation

Not every household needs reverse osmosis, and it should not be viewed as a universal solution for every water-quality concern.

Whole-House vs. Point-of-Use Treatment

Homeowners often ask whether they need to treat all the water entering the home or only the water used for drinking.

The answer depends on several considerations, including:

Household needs
Water-use patterns
The contaminants identified
Budget
Plumbing configuration

A qualified treatment professional can help determine whether a point-of-use system, a whole-house system, or another approach best fits the property’s needs.

Look for Independent Certification

When comparing treatment systems, look beyond advertising claims.

Products that have been independently tested and certified to recognized performance standards, such as NSF/ANSI drinking water treatment standards, provide greater confidence that the equipment has been evaluated under established testing protocols.

Certification does not guarantee performance under every condition, but it provides an important basis for comparing products.

Don’t Skip Post-Treatment Testing

Installing a treatment system is not the final step.

Follow-up laboratory testing helps confirm that the system is performing as intended.

Verification testing is particularly important:

After installing new treatment equipment
After replacing major components
After significant maintenance
If water quality changes
As recommended by the treatment professional

Without post-treatment testing, there is no reliable way to confirm treatment performance.

Test First. Treat Second.

One of the biggest mistakes homeowners make is buying a filter before understanding what’s actually in their water.

PFAS may not be the only issue identified during testing. Depending on the laboratory results, additional findings could require different responses—or no treatment at all.

For example, some water-quality concerns are addressed with treatment equipment, while others may require investigation of the well, plumbing, or surrounding conditions.

That’s why professional sampling and comprehensive laboratory testing are valuable before making treatment decisions.

Nantucket Well Water Sampling LLC collects water samples at private properties across Nantucket and coordinates laboratory analysis with certified laboratories. Clients receive their laboratory reports digitally, providing the information needed to discuss any treatment options with qualified professionals.

Frequently Asked Questions

Can I tell if my well has PFAS by taste or smell?
No. PFAS generally cannot be detected by taste, smell, or appearance. Laboratory testing is required.

Should I buy a filter before testing?
Testing first is the better approach. Laboratory results help determine whether treatment is appropriate and what type of treatment may be suitable.

Is reverse osmosis better than activated carbon?
Neither technology is universally “better.” Both may reduce many PFAS compounds when properly selected, installed, and maintained. The appropriate choice depends on the laboratory results, household needs, and system design.

If my neighbor’s well tested for PFAS, does mine have it too?
Not necessarily. Private wells can differ significantly, even within the same neighborhood. Every well should be evaluated individually.

Does municipal-water testing tell me what’s in my private well?
No. The Town of Nantucket notes that most private residential wells draw from the upper unconfined aquifer, while several municipal wells draw from deeper groundwater separated by a confining unit. Municipal results should not be used as proof of an individual private well’s water quality.

Final Thoughts

Receiving a PFAS laboratory result doesn’t have to be overwhelming.

The most effective approach is straightforward:

Test your well.
Understand the laboratory findings.
Discuss treatment options with a qualified water-treatment professional if appropriate.
Verify treatment performance with follow-up laboratory testing.

Every private well is different, and treatment decisions should be based on reliable laboratory data—not assumptions or generalized information.

If you need water testing for a Nantucket property, schedule a professional well-water sampling appointment with Nantucket Well Water Sampling LLC. The company collects the sample, coordinates analysis with a certified laboratory, and provides your laboratory report so you can make informed decisions about your water.

Book an Appointment · Learn more about our services, how sampling works, or get in touch with questions.

Sources

MassDEP — PFAS in Private Well Drinking Water Supplies FAQ
Town of Nantucket — FAQ: Does the aquifer that the Island gets groundwater from…
Town of Nantucket — PFAS Updates
U.S. EPA — Per- and Polyfluoroalkyl Substances (PFAS)
NSF/ANSI Drinking Water Treatment Standards (independent product certification)

This article is educational and is not a substitute for guidance from MassDEP, the Nantucket Health Department, or a qualified water-treatment professional. Treatment decisions should be based on your specific laboratory results.

PFAS in a Nantucket Private Well: What Your Test Result Means—and What to Know Before Buying a Filter