We read 24 results from Washington Suburban Sanitary Commission’s 2025 water quality report. No results over a legal limit; 6 above a health goal or guideline.
Serves about 1,900,000 people · Water system ID MD0150005 · Read the district’s 2025 report (opens in a new tab)
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Results from the 2025 report
Each number is copied from the district’s report and links to the page it’s printed on. Where the report lists several plants, wells or purchased water, the highest is shown.
| Contaminant | Result | Health goal | Legal limit | What it means |
|---|---|---|---|---|
| Gross alpha (radioactivity)highest measured · range ND to 3.2 · Potomac plant, highest of 2 sources · 2025 report, page 12 | 3.2 pCi/L | 0 pCi/L | 15 pCi/L | Above the health goalThe health goal is zero |
| Gross beta (radioactivity)highest measured · range ND to 6.1 · Potomac plant, highest of 2 sources · 2025 report, page 12 | 6.1 pCi/L | 0 pCi/L | 50 pCi/L | Above the health goalThe health goal is zero |
| PFOA (a PFAS)highest measured · range 1.8 to 3.7 · Potomac plant, highest of 2 sources · 2025 report, page 14 | 3.7 ppt | 0.007 ppt | 4 ppt from 2029 | Above the health goal529x the health goal |
| PFOS (a PFAS)highest measured · range 1.9 to 4.2 · Potomac plant, highest of 2 sources · 2025 report, page 14 | 4.2 ppt | 1 ppt | 4 ppt from 2029 | Above the federal limit that takes effect in 20291.1x the 4 ppt federal limit that takes effect in 2029Not a violation yet: EPA's 4 ppt limit is final, but water systems don't have to meet it until 2029. |
| Radium-228highest measured · range 0.3 to 0.5 · Potomac plant, highest of 2 sources · 2025 report, page 12 | 0.5 pCi/L | 0.02 pCi/L | 5 pCi/L | Above the health goal26x the health goal |
| Total coliform bacteriahighest month · range ND to 0.5 · Distribution system · 2025 report, page 13 | 0.5 % positive | 0 % positive | 5 % positive | Above the health goalThe health goal is zero |
| Bariumhighest measured · range 0.03 to 0.05 · Potomac plant, highest of 2 sources · 2025 report, page 11 | 0.05 ppm | 2 ppm | 2 ppm | Below the health goal |
| Chlorinehighest running annual average · range 0.02 to 2.11 · Distribution system · 2025 report, page 13 | 1.05 ppm | None set | 4 ppm | Below the legal limit |
| Copper90th percentile of 69 homes tested, 0 over the action level · sampled 2023 · Customer taps (69 homes) · 2025 report, page 13 | 0.12 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (HAA5)highest running annual average · range 16 to 79 · Distribution system · 2025 report, page 13 | 48 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · range 14 to 102 · Distribution system · 2025 report, page 13 | 66 ppb | None set | 80 ppb | Below the legal limit |
| E. colias reported · Distribution system · 2025 report, page 13 | Not detected | 0 positive samples | 0 positive samples | Not detected |
| Fluoridehighest measured · range 0.5 to 0.95 · Patuxent plant · 2025 report, page 11 | 0.95 ppm | 1 ppm | 4 ppm | Below the health goal |
| Lead90th percentile of 69 homes tested, 0 over the action level · sampled 2023 · Customer taps (69 homes) · 2025 report, page 13 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Nitrate (as N)highest measured · range 0.5 to 1.6 · Potomac plant, highest of 2 sources · 2025 report, page 11 | 1.6 ppm | 10 ppm | 10 ppm | Below the health goal |
| PFHxS (a PFAS)highest measured · range ND to 1.9 · Potomac plant, highest of 2 sources · 2025 report, page 14 | 1.9 ppt | None set | 10 ppt from 2029 | Below the legal limit |
| PFNA (a PFAS)highest measured · range ND to 1.7 · Potomac plant, highest of 2 sources · 2025 report, page 14 | 1.7 ppt | None set | 10 ppt from 2029 | Below the legal limit |
| Turbidity (cloudiness)highest monthly average · range 0.02 to 0.24 · Potomac plant, highest of 2 sources · 2025 report, page 12 | 0.06 NTU | None set | 1 NTU | Below the legal limit |
| PFBA (a PFAS)average · range 2.5 to 4.2 · Potomac plant, highest of 2 sources · 2025 report, page 15 | 3.3 ppt | None set | None | No health limit |
| PFBS (a PFAS)highest measured · range 2.4 to 3 · Potomac plant, highest of 2 sources · 2025 report, page 14 | 3 ppt | None set | None | No health limit |
| PFHpA (a PFAS)average · range ND to 2.1 · Potomac plant, highest of 2 sources · 2025 report, page 15 | 1 ppt | None set | None | No health limit |
| PFHxA (a PFAS)average · range 2.8 to 4.6 · Potomac plant, highest of 2 sources · 2025 report, page 15 | 3.7 ppt | None set | None | No health limit |
| PFPeA (a PFAS)average · range 3.4 to 4.3 · Potomac plant, highest of 2 sources · 2025 report, page 15 | 3.8 ppt | None set | None | No health limit |
| Sodiumaverage · range 11 to 34 · Potomac plant, highest of 2 sources · 2025 report, page 15 | 22 ppm | None set | None | No health limit |
Utility results describe the whole system, measured where water enters the pipes, not your tap. Your home’s plumbing can add lead or copper. 1 number we weren’t sure about is held back until a person checks.
What you can do
Nothing here is an emergency notice: if the district has a violation, it must tell customers directly. If you’d like to lower these at your tap, these are the treatments that remove them, and the catalog shows the models certified for each. Ranking is by certified removal; commissions never change the order.
Radium and uranium
Found: Gross alpha (radioactivity), Gross beta (radioactivity), Radium-228
What removes it: Reverse osmosis.
PFAS ("forever chemicals")
Found: PFOA (a PFAS), PFOS (a PFAS)
What removes it: Reverse osmosis.
Bacteria and viruses
Found: Total coliform bacteria
What removes it: UV purification (and tell your utility).
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