Is Gaithersburg, MD tap water safe?
Data: U.S. EPA · How we read the data · How we check it
Summary
No federal limits exceeded in EPA data for Washington Suburban Sanitary Commission. 2 PFAS were detected below the limits.
Washington Suburban Sanitary Commission supplies Gaithersburg (1.9 million people).
Water system
Washington Suburban Sanitary Commission
1.9 million people · Surface water · EPA ID MD0150005
| PFAS | Highest average | Limit |
|---|---|---|
| PFOA Not detected | – | 4 ppt |
| PFOS Not detected | – | 4 ppt |
| PFHxS Not detected | – | 10 ppt |
| PFNA Not detected | – | 10 ppt |
| HFPO-DA (GenX) Not detected | – | 10 ppt |
ppt = parts per trillion. "Highest average" is the highest average at any of the system's entry points, the way EPA compares results with the limits.
Lead: 0 ppb at the 90th percentile (Dec 2020, and 9 in 10 homes sampled were at or below it) No results since 2020
Health-based violations since 2016: 0
Across Maryland, 13 of 76 water systems EPA tested had PFAS above a 2024 federal limit, and 1 system were above the lead action level in results from the last five years. Maryland results.
Gaithersburg homes and lead pipes
Lead service lines and lead solder were allowed until 1986, so homes from before then are the ones to check. Renting? Ask your landlord what the service line is made of, because it's their pipe to replace. How to check your own line.
Housing: Census American Community Survey 2020–2024 5-year estimates for Gaithersburg city (tables B25034, B25003). Estimates for small places have a margin of error.
How nearby cities compare
| City | PFAS | Lead (90th pct.) |
|---|---|---|
| Rockville 5 mi Washington Suburban Sanitary Commission | None above limits | – |
| College Park 17 mi Washington Suburban Sanitary Commission | None above limits | – |
| Laurel 18 mi Washington Suburban Sanitary Commission | None above limits | – |
| Frederick 23 mi New Design – Frederick County Water System | None above limits | – |
| Bowie 28 mi Washington Suburban Sanitary Commission | None above limits | – |
| Baltimore 33 mi City of Baltimore | None above limits | 2.74 ppb |
Gaithersburg ZIP codes (2)
- 20877
- 20878
Questions
Is Gaithersburg tap water safe to drink?
Washington Suburban Sanitary Commission has had no health-based violations since 2016. Utility data can't show lead from your own pipes: if your home was built before 1986, test your tap. Your utility's annual Consumer Confidence Report is the official summary.
Who supplies water in Gaithersburg, MD?
Washington Suburban Sanitary Commission, which serves 1.9 million people.
Does Gaithersburg tap water have PFAS?
Washington Suburban Sanitary Commission had 2 PFAS detected at least once in EPA's 2023–2025 testing, all with averages below the federal limits.
Do Gaithersburg homes have lead pipes?
Census estimates put 32% of Gaithersburg homes as built before 1980 (Maryland: 51%). Lead service lines and lead solder were allowed until 1986, so older homes are more likely to have them. Washington Suburban Sanitary Commission's service line inventory says what your line is made of. The only way to know for your home is to check the line where it enters the house and test your tap.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.