Delaware County, Pennsylvania: drinking water report. Delaware County borders Philadelphia to the southwest, home to about 580,000 residents.
Delaware County borders Philadelphia to the southwest, home to about 580,000 residents. Aqua Pennsylvania serves the largest portion of the county, supplemented by the Chester Water Authority (drawing from Octoraro Reservoir) and several smaller systems. Surface water from the Delaware River and local streams provides the primary supply, though some communities use groundwater.
Delaware County's industrial history along the Delaware River waterfront – refineries, shipyards, chemical plants – has left contamination in soils and groundwater that persists today. UCMR5 data shows PFAS detections in multiple county water systems. The proximity to Philadelphia's industrial corridor and the former Philadelphia Naval Shipyard adds to the regional contamination picture.
According to the Pennsylvania DEP's 2024 monitoring data, three Delaware County water systems reported PFAS above state-proposed MCLs. Pennsylvania's proposed limits of 14 ppt for PFOA and 18 ppt for PFOS would require treatment upgrades at several facilities.
Delaware County's mix of providers means your water quality depends on which system serves your home. Communities on the Delaware River face different risks than those drawing from western county groundwater.
Check your water to see data for your provider. A reverse osmosis system handles the broadest range of contaminants. Our water filter guide covers certified options. Pull your detailed report, and visit our Pennsylvania page for statewide data.
Drinking water is one exposure route. These federal datasets also cover Delaware County, PA.
The EPA places Delaware 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.
80% of homes in Delaware County, PA were built before 1980, and 35% 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 Delaware County, PA averages 8.2 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