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Updated 2026-10-15
County water report

Montgomery County Water Quality: 5 Cities Ranked by the Records

Montgomery County, Pennsylvania: 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 Montgomery 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.

Perfluorooctanesulfonic acid (PFOS)Detected in 3 systems of 5 tested4.0 ng/L federal MCL (2024) · US EPAHighest33.8 ng/L
Perfluorooctanoic acid (PFOA)Detected in 3 systems of 5 tested4.0 ng/L federal MCL (2024) · US EPAHighest17.5 ng/L
LithiumDetected in 5 systems10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest22.4 µg/L
Perfluorononanoic acid (PFNA)Detected in 2 systems of 5 tested10 ng/L federal MCL (2024) · US EPAHighest13.5 ng/L
Perfluorohexanesulfonic acid (PFHxS)Detected in 3 systems of 5 tested10 ng/L federal MCL (2024) · US EPAHighest10.6 ng/L
Lead (90th percentile)Detected in 4 systems of 5 tested15 µg/L federal action level · US EPAHighest2.3 µg/L
Perfluorobutanesulfonic acid (PFBS)Detected in 5 systems2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest9.2 ng/L
Perfluorohexanoic acid (PFHxA)Detected in 5 systems400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest12.2 ng/L
4 more contaminants detectedShow
1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)Detected in 1 system of 5 testedNo federal or state limit; shown for transparencyHighest6 ng/L
Perfluorobutanoic acid (PFBA)Detected in 5 systemsNo federal or state limit; shown for transparencyHighest41.4 ng/L
Perfluoroheptanoic acid (PFHpA)Detected in 3 systems of 5 testedNo federal or state limit; shown for transparencyHighest9 ng/L
Perfluoropentanoic acid (PFPeA)Detected in 5 systemsNo federal or state limit; shown for transparencyHighest65.3 ng/L
19 PFAS tested, none detected in any systemShow

Tested in these 5 systems: AMBLER BORO WATER DEPT, HORSHAM WATER&SEWER AUTHORITY, NORTH WALES WATER AUTHORITY, PA AMERICAN NORRISTOWN, POTTSTOWN BOROUGH WATER AUTH

  • 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)
  • 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)
  • 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 Montgomery County3 of 5 city reports had a PFAS sample above a 2024 EPA limit
  1. Horsham33.8 ng/L
  2. Ambler13.7 ng/L
  3. North Wales11.1 ng/L
4.0 ng/L federal MCL · PFOS, ng/LPFAS in Pennsylvania
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 Pennsylvania
Who supplies the county

Largest water systems

  1. NorristownPA AMERICAN NORRISTOWN · PA1460046
    88,885 served
  2. North WalesNORTH WALES WATER AUTHORITY · PA1460048
    72,496 served
  3. PottstownPOTTSTOWN BOROUGH WATER AUTH · PA1460037
    36,000 served
  4. HorshamHORSHAM WATER&SEWER AUTHORITY · PA1460033
    26,000 served
  5. AmblerAMBLER BORO WATER DEPT · PA1460020
    20,000 served
Questions

Frequently asked

How does Montgomery County tap water compare across cities?

PurityMap ranks 5 cities in Montgomery 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 Norristown's main water system: PA AMERICAN NORRISTOWN · PWSID PA1460046 · Purity Score 98 (Excellent) · 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 Montgomery County cities had a PFAS sample above a 2024 EPA limit?

3 of 5 Montgomery County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Horsham (PFOS 33.8 ng/L), Ambler (PFOA 15.3 ng/L), North Wales (PFOA 13 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 Montgomery County tap water?

Utilities report lead as a 90th-percentile result from home taps. 4 of 5 Montgomery 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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