Montgomery County borders Philadelphia to the northwest, serving about 840,000 residents.
Montgomery County borders Philadelphia to the northwest, serving about 840,000 residents. Water comes from multiple providers – Aqua Pennsylvania, the former Horsham Water and Sewer Authority, North Penn Water Authority, and several others – drawing from the Schuylkill River, local groundwater, and purchased Philadelphia Water Department supplies. The county's proximity to former military installations makes PFAS a defining water quality issue.
Montgomery County is ground zero for one of the most significant PFAS contamination events in the Mid-Atlantic. The former Naval Air Station Joint Reserve Base Willow Grove and the Horsham Air Guard Station used AFFF extensively, contaminating groundwater that fed public and private drinking water wells across a wide area.
According to the Pennsylvania DEP, over a dozen public water systems in Montgomery County have detected PFAS above state-proposed MCLs. North Penn Water Authority spent over $20 million installing treatment to address PFAS in its wells. The Navy has funded alternative water connections for the most affected areas, but remediation of the groundwater plume will take decades.
If you are in the Horsham, Warminster, or Willow Grove area, PFAS contamination is well-documented and your utility has likely installed treatment. But treatment systems vary in effectiveness across different PFAS compounds.
Check your water for the latest monitoring data from your provider. A reverse osmosis system provides comprehensive household-level PFAS removal. Our water filter guide covers certified options. Pull your detailed report, and visit our Pennsylvania page for statewide patterns.
Drinking water is one exposure route. These federal datasets also cover Montgomery County, PA.
The EPA places Montgomery County, PA in Zone 1 - the EPA's highest-risk category, where the predicted average indoor radon level is above 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
63% of homes in Montgomery County, PA were built before 1980, and 22% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Montgomery County, PA averages 8.5 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide
27 public water systems serving Montgomery County, PA have EPA lead testing on record. The reported lead sample skews toward systems that already flagged a problem, so its exceedance rate is not directly comparable with other areas. 22 water systems serving Montgomery County, PA carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Ground Water Rule | 12 |
| Revised Total Coliform Rule | 4 |
| Surface Water Treatment Rule | 3 |
| Haloacetic Acids (HAA5) | 2 |
| Lead and Copper Rule | 2 |
Source: EPA Lead and Copper Rule 90th-percentile tap sampling and EPA SDWIS Safe Drinking Water Act enforcement records, aggregated from the public water systems serving this county. Figures are counts of water systems, not a test of any individual home or tap.