Chester County, Pennsylvania: drinking water report. Chester County lies west of Philadelphia, home to about 540,000 residents.
Chester County lies west of Philadelphia, home to about 540,000 residents. Water comes from multiple providers – Aqua Pennsylvania, the Chester Water Authority, and numerous small community systems – drawing from the Brandywine Creek, other surface sources, and local groundwater. The county is a mix of affluent suburbs, small towns, and active farmland, all of which influence water quality.
Chester County's water quality varies significantly by provider and source. Agricultural activity in the western part of the county contributes nitrate to shallow groundwater. UCMR5 data shows PFAS detections in several county systems, though at lower concentrations than in neighboring Montgomery and Bucks counties, which host former military PFAS sources.
According to the Pennsylvania DEP's 2024 monitoring data, two Chester County water systems reported PFAS above state-proposed MCLs. The county does not have the concentrated military contamination seen in its neighbors, but diffuse PFAS from commercial and industrial sources is still present.
Chester County benefits from the absence of major military PFAS sources, but agricultural contamination and general PFAS presence are still worth tracking.
Check your water for data specific to your provider. For nitrate in rural areas, reverse osmosis is the most effective treatment. For PFAS, activated carbon or RO both work. Our water filter guide covers both scenarios. Pull your detailed report, and visit our Pennsylvania page for statewide data.
Drinking water is one exposure route. These federal datasets also cover Chester County, PA.
The EPA places Chester 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.
46% of homes in Chester County, PA were built before 1980, and 16% 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 Chester County, PA averages 8.4 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
25 public water systems serving Chester 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. 33 water systems serving Chester County, PA carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Ground Water Rule | 26 |
| Lead and Copper Rule | 7 |
| Revised Total Coliform Rule | 4 |
| Lead and Copper Rule Revisions | 1 |
| Coliform (pre-TCR) | 1 |
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.