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What 'Detected,' 'Median,' and 'Range' Mean in Portsmouth's PFAS Sampling Record

'Detected' Levels Indicate Measured Presence, Not Safety or Violation

The EPA’s 2023–2024 Unregulated Contaminant Monitoring Rule found various PFAS compounds were measured in Portsmouth’s public water system. A detection means the compound was measured above the reporting level during sampling. This does not mean the water is unsafe or that federal health standards were violated. For example, PFOA was detected in some samples but never reached the federal limit established for 2024.

'Median' Represents the Middle Value of Detections, Not an Average for Every Home

The median figure reported for PFAS levels shows the midpoint of detected measurements in the system’s samples. It does not predict your household’s exact water level because individual usage and plumbing will vary.

'Range' Reflects the Highest and Lowest Detected Values, Not a Regulatory Threshold

Range values provide the spread between the lowest and highest PFAS measurements found in the system samples during the monitoring period. This gives an idea of variability but is not a safety limit or guarantee of your own water’s quality.

What You Should Write Down Before Seeking Advice on PFAS Treatment

Obtain Your Home’s Recent Water Test Result for PFAS Compounds

Your home’s specific water test is essential. Public system data does not measure individual household water conditions, so knowing your own water’s PFAS concentrations will guide treatment needs.

Note Any Current Water Treatment Equipment and Its Capabilities

Document your existing treatment system type and its maintenance history. Knowing this will help identify whether additional or specialized filtration is required.

Record Any Water Quality Concerns Beyond PFAS

Listing any taste, staining, or other water issues may assist in selecting a treatment option that addresses multiple concerns.

Example Interpretation of Portsmouth’s PFAS Data for a Homeowner

PFOA Detected Up to 0.007 µg/L with Median 0.005 µg/L: Below Federal MCL 4.0 ng/L

Sampling found PFOA in some system water at amounts below the 2024 federal maximum contaminant level. This suggests the public water system has low-level presence, but your water could differ.

PFOS Seen in Fewer Samples, Maximum 0.005 µg/L, Also Below Federal MCL

The PFOS compound was found less often and at similarly low levels, with no recorded health-based violation for Portsmouth Water Works.

Other PFAS Compounds Show Detected but Low Concentrations

PFHxS, PFBS, PFHxA, and others appeared at very low levels, none exceeding health standards or exceeding federal limits for 2024.

Distinguishing PFAS Presence From Commonly Confused Household Water Issues

PFAS Are Persistent Synthetic Chemicals, Not Related to Hardness or Iron

Unlike mineral-based water problems, PFAS are man-made compounds that require specialized filtration technology to reduce, as typical water conditioners or softeners do not address them.

Detected PFAS Does Not Indicate Typical Taste or Odor Problems

PFAS compounds do not cause taste or smell changes, so other equipment may be needed for those issues beyond PFAS filtration.

How Public Water System Records Differ From Private Well PFAS Testing

System Data Reflects Averages From Multiple Sampling Points, Not Your Individual Tap

Public water sampling in Portsmouth covers a broad population and multiple locations, so it cannot establish your home’s exact PFAS concentration.

Private Well Testing Provides Home-Specific PFAS Levels Critical for Treatment Decisions

Only a private well test or sample from your tap can confirm actual PFAS levels requiring targeted filtration for your household.

Public System Absence of Health-Based Violations Indicates Regulatory Compliance

Portsmouth Water Works’ record shows zero EPA health-based violations, reflecting compliance with federal water safety standards despite detections.

Final Step: Selecting Targeted Filtration to Match Your Measured Need

For households whose current equipment cannot keep up with PFAS levels, a targeted solution like the Fleck PFAS Forever Chemicals Filter ships ready to configure. This system is designed to reduce PFAS compounds effectively when sized and operated according to your home’s specific water test results.

Where this information comes from

Source: EPA SDWIS public water system record. Sampled 2024-05-10. These figures describe the public water system's record, not the plumbing inside any individual building.

On record: EPA UCMR5 monitoring (2023-2025) for PORTSMOUTH WATER WORKS (NH1951010), NH: 180 results across 10 listed contaminants, 30 detections above the reporting level; 5 results above a 2024 federal MCL