Montgomery County, Maryland: drinking water report. Montgomery County borders Washington, DC to the north and west, home to about 1.06 million residents.
Montgomery County borders Washington, DC to the north and west, home to about 1.06 million residents. The Washington Suburban Sanitary Commission (WSSC Water) is the primary provider, drawing from the Potomac River and Patuxent River. WSSC operates two major treatment plants – Potomac in Potomac, MD and Patuxent in Laurel, MD – together serving about 1.8 million people across Montgomery and Prince George's counties.
The Potomac River watershed is heavily utilized, receiving treated wastewater and stormwater from communities across Virginia, West Virginia, Maryland, and DC. Despite this, WSSC Water has maintained a strong compliance record. UCMR5 data shows low-level PFAS detections in the WSSC system.
According to the Maryland Department of the Environment's 2024 monitoring data, PFAS levels in the WSSC system were below proposed federal MCLs. The more significant water quality dynamic in Montgomery County is seasonal – heavy rainfall events flush agricultural and urban runoff into the Potomac, increasing turbidity and organic content that drives up disinfection byproduct levels during treatment. WSSC has invested in ozone treatment to reduce reliance on chlorine.
Montgomery County benefits from a well-funded, well-managed utility, but seasonal water quality variation is real. Spring and summer storms can shift the contaminant profile temporarily.
Check your water for the latest data in your area. An activated carbon filter improves taste and reduces chlorine and DBPs. For PFAS, reverse osmosis provides additional protection. Our water filter guide covers both options. Pull your detailed report, and visit our Maryland page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Montgomery County, MD.
The EPA places Montgomery County, MD 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.
50% of homes in Montgomery County, MD were built before 1980, and 9% 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, MD averages 7.5 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