Data & Methodology — Montgomery County

Full contaminant data, sample history, and sourcing for Montgomery County. For readers who want to go beyond the summary.

Contaminant Data — All Analytes

418 well testing events on record, covering 22 analytes. Data spans 1925 to 2024.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. PA Avg
PFOA municipal 780 2023–2025 65%
175% of limit ↑ 87% above
PFOS municipal 780 2023–2025 58%
160% of limit ↑ 26% above
Radon 60 1986–2023 100%
16% of limit ↓ 88% below
Arsenic 79 1979–2023 77%
40% of limit ↑ 37% above
Manganese 126 1956–2023 71%
6% of limit ↓ 99% below
Iron 149 1925–2023 72%
18% of limit ↓ 97% below
Sulfate 152 1925–2023 100%
10% of limit ↓ 39% below
Nitrate 142 1925–2023 99%
33% of limit ↑ 85% above
Fluoride 142 1949–2023 56%
2% of limit ↓ 44% below
PFNA municipal 231 2023–2025 6%
70% of limit ~ typical
Chloride 152 1925–2023 100%
8% of limit ↓ 23% below
PFHxS municipal 231 2023–2025 19%
41% of limit ~ typical
HFPO-DA (GenX) municipal 552 2023–2025 0%
— —
Lead 92 1974–2023 68%
3% of limit ↓ 46% below
Nitrite 94 1979–2023 11%
1% of limit ↓ 47% below
Uranium 81 1986–2023 85%
10% of limit ↑ 340% above
E. coli 4 2000–2021 38%
— ~ typical
Hardness 152 1925–2023 100%
— ↑ 29% above
PFBS municipal 554 2023–2025 67%
— ~ typical
pH 173 1949–2023 100%
— ~ typical
Sodium 133 1925–2023 100%
— ~ typical
Total Coliform 4 2000–2021 67%
— ~ typical

Distribution shows the share of samples in each concentration band relative to the EPA Maximum Contaminant Level (MCL): Low = below half the MCL, Moderate = between half and the MCL, High = above the MCL. Analytes without an MCL (e.g. sodium, pH) show — in the limit columns. State average is based on county median values across PA.

Compare your result with Montgomery County

Of the 79 arsenic tests on record for Montgomery County (1979–2023), 23% found none, and half were below 2.5 µg/L.

Of the 152 chloride tests on record for Montgomery County (1925–2023), 0% found none, and half were below 20.5 mg/L.

Of the 142 fluoride tests on record for Montgomery County (1949–2023), 44% found none, and half were below 40 µg/L.

Of the 149 iron tests on record for Montgomery County (1925–2023), 28% found none, and half were below 15 µg/L.

Of the 92 lead tests on record for Montgomery County (1974–2023), 32% found none, and half were below 0.177 µg/L.

Of the 126 manganese tests on record for Montgomery County (1956–2023), 29% found none, and half were below 0.38 µg/L.

Of the 142 nitrate tests on record for Montgomery County (1925–2023), 1% found none, and half were below 3.23 mg/L.

Of the 549 pfoa tests on record for Montgomery County (2025), 32% found none, and half were below 4.55 ng/L.

Of the 549 pfos tests on record for Montgomery County (2025), 38% found none, and half were below 3.5 ng/L.

Of the 152 sulfate tests on record for Montgomery County (1925–2023), 0% found none, and half were below 25.9 mg/L.

Of the 81 uranium tests on record for Montgomery County (1986–2023), 15% found none, and half were below 2.89 µg/L.

Have a number from your lab? Enter it to see where it falls. Nothing is sent anywhere.

Want the full picture for your well? Check all your results.

Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • PFOA 780 samples
  • PFOS 780 samples
  • Radon 60 samples
  • Arsenic 79 samples
  • Manganese 126 samples
  • Iron 149 samples
  • Sulfate 152 samples
  • Nitrate 142 samples
  • Fluoride 142 samples
  • Chloride 152 samples
  • HFPO-DA (GenX) 552 samples
  • Lead 92 samples
  • Nitrite 94 samples
  • Uranium 81 samples
  • Hardness 152 samples
  • PFBS 554 samples
  • pH 173 samples
  • Sodium 133 samples

Limited data (<15 samples) — interpret with caution

  • E. coli 4 samples
  • Total Coliform 4 samples

Public vs. Private Water in Montgomery County

170 Active public water systems
1,274,288 Residents on public water
20% Households on private wells

Public water systems in Montgomery County are regulated by the EPA and must test and report contaminant levels. Private well owners are responsible for their own testing — there is no routine monitoring of private wells by any government agency.

CDC Health Outcome Correlations

Where contaminants detected in Montgomery County have established associations with specific health outcomes, we cross-reference CDC PLACES county-level prevalence data. This is a contextual signal, not a causal claim.

Contaminant Associated Condition Montgomery County Prevalence PA Average Source Year
Arsenic Cancer prevalence 7.3% 7.0% 2020
Lead Heart disease rate 6.1% 7.2% 2020
Arsenic Kidney disease rate 2.2% 3.0% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Montgomery County CDC PLACES data →

Data Sources

This report aggregates data from the following public databases:

Methodology

Raw records are downloaded from the Water Quality Portal and normalized to µg/L (ppb). Records are deduplicated by sample ID and date, and certified outliers are excluded. Analyte names are mapped to EPA canonical forms. Detection rates, distribution bands, and MCL comparisons are computed from the normalized dataset.

Distribution bands use the EPA Maximum Contaminant Level as the threshold: concentrations below 50% of the MCL are classed as Low, between 50% and 100% as Moderate, and above 100% as High. For analytes without an MCL (sodium, hardness, pH), distribution is not computed.

State comparison uses the median of county median values across all counties in PA with at least one sample for that analyte.

Last updated: 2026-08-04

Full methodology →