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Updated 2026-10-15
County water report

Rockingham County Water Quality: 5 Cities Ranked by the Records

Rockingham County, New Hampshire: 5 city reports built from EPA and utility records. A county has many suppliers; each city shows the system that serves it.

Find my systemOpen on the mapPrivate wells in Rockingham County
Across the county's systems

Highest result for each contaminant

One row per contaminant: the highest result any system in the county reported, against its limit. Open a row for the systems behind it.

Perfluorooctanoic acid (PFOA)Detected in 5 systems4.0 ng/L federal MCL (2024) · US EPAHighest8.5 ng/L
Perfluorooctanesulfonic acid (PFOS)Detected in 3 systems of 5 tested4.0 ng/L federal MCL (2024) · US EPAHighest5.3 ng/L
LithiumDetected in 1 system of 5 tested10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest10 µg/L
  • PORTSMOUTH WATER WORKS10 µg/LSample date: 2023-07-18 to 2024-05-10
  • DERRY WATER DEPTNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-01-03 to 2024-10-02
  • EXETER WATER DEPTNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-01-04 to 2024-10-08
  • SALEM WATER DEPTNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-12-12 to 2025-09-09
  • SEABROOK WATER DEPTNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-01-03 to 2024-07-09
Perfluorohexanesulfonic acid (PFHxS)Detected in 1 system of 5 tested10 ng/L federal MCL (2024) · US EPAHighest5 ng/L
  • PORTSMOUTH WATER WORKS5 ng/LSample date: 2023-07-18 to 2024-05-10
  • DERRY WATER DEPTNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-31 to 2024-10-02
  • EXETER WATER DEPTNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-04 to 2024-10-08
  • SALEM WATER DEPTNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-12-12 to 2025-09-09
  • SEABROOK WATER DEPTNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-03-06 to 2024-08-20
Lead (90th percentile)Detected in 2 systems of 5 tested15 µg/L federal action level · US EPAHighest3 µg/L
Perfluorobutanesulfonic acid (PFBS)Detected in 2 systems of 5 tested2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest9 ng/L
Perfluorohexanoic acid (PFHxA)Detected in 4 systems of 5 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest6 ng/L
Perfluorobutanoic acid (PFBA)Detected in 2 systems of 5 testedNo federal or state limit; shown for transparencyHighest13 ng/L
2 more contaminants detectedShow
Perfluoroheptanoic acid (PFHpA)Detected in 2 systems of 5 testedNo federal or state limit; shown for transparencyHighest3 ng/L
Perfluoropentanoic acid (PFPeA)Detected in 3 systems of 5 testedNo federal or state limit; shown for transparencyHighest7 ng/L
21 PFAS tested, none detected in any systemShow

Tested in these 5 systems: DERRY WATER DEPT, EXETER WATER DEPT, PORTSMOUTH WATER WORKS, SALEM WATER DEPT, SEABROOK WATER DEPT

  • 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)
  • 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS)
  • 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS)
  • 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)
  • 4,8-Dioxa-3H-perfluorononanoic acid (ADONA)
  • 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS)
  • Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals)
  • N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)
  • N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA)
  • Nonafluoro-3,6-dioxaheptanoic acid (NFDHA)
  • Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA)
  • Perfluoro-3-methoxypropanoic acid (PFMPA)
  • Perfluoro-4-methoxybutanoic acid (PFMBA)
  • Perfluorodecanoic acid (PFDA)
  • Perfluorododecanoic acid (PFDoA)
  • Perfluoroheptanesulfonic acid (PFHpS)
  • Perfluorononanoic acid (PFNA)
  • Perfluoropentanesulfonic acid (PFPeS)
  • Perfluorotetradecanoic acid (PFTA)
  • Perfluorotridecanoic acid (PFTrDA)
  • Perfluoroundecanoic acid (PFUnA)
5 cities

Cities ranked by the records

Showing 5 of 5 cities · scores are system-level, not tap tests

Ranked by the Purity Score of each city's main water system, highest first. Scores belong to water systems; there is no county score. The score is computed only from contaminants measured in the published EPA record, so this ranks the record, not which city's water is safest. How the score works.

PFAS in Rockingham County5 of 5 city reports had a PFAS sample above a 2024 EPA limit
  1. Seabrook5.3 ng/L
  2. Portsmouth5 ng/L
  3. Exeter4 ng/L
4.0 ng/L federal MCL · PFOS, ng/LPFAS in New Hampshire
Lead

0of 5 cities above the 15 µg/L action level

Based on each system's 90th-percentile result. Lead from household plumbing isn't in this record.

Lead in New Hampshire
Who supplies the county

Largest water systems

  1. PortsmouthPORTSMOUTH WATER WORKS · NH1951010
    33,000 served
  2. SalemSALEM WATER DEPT · NH2051010
    21,080 served
  3. DerryDERRY WATER DEPT · NH0611010
    17,528 served
  4. SeabrookSEABROOK WATER DEPT · NH2111010
    14,000 served
  5. ExeterEXETER WATER DEPT · NH0801010
    12,236 served
Questions

Frequently asked

How does Rockingham County tap water compare across cities?

PurityMap ranks 5 cities in Rockingham County by the Purity Score of each city's main water system, computed only from contaminants measured in the published EPA record. Scores belong to water systems, not to cities. The highest published score is Derry's main water system: DERRY WATER DEPT · PWSID NH0611010 · Purity Score 76 (Good) · Confidence: moderate · Assessed at the water-system level. The ranking compares the records, not which city's water is safest, and your own tap can differ with household plumbing.

How many Rockingham County cities had a PFAS sample above a 2024 EPA limit?

5 of 5 Rockingham County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Salem (PFOA 8.5 ng/L), Seabrook (PFOA 8 ng/L), Portsmouth (PFOA 7 ng/L). That limit is judged on a yearly average, and water systems have until 2029 to meet it, so a single sample is not a violation. PFAS were detected at any level in 5.

Is there lead in Rockingham County tap water?

Utilities report lead as a 90th-percentile result from home taps. 2 of 5 Rockingham County cities reported a value above zero, and none was above the 15 µg/L federal action level. Lead usually comes from a building's own pipes and fixtures, so only a test at your tap tells you what you drink.

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