Potomac, MD tap water
Supplied by Washington Suburban Sanitary Commission. Here's what its water means for your fish.
Disinfectant
Chlorine
Your water is treated with chlorine. It slowly gases off from standing water, and any water conditioner removes it.
Safety for fish and shrimp
Nitrite (NO₂)
Not detected (Low)
Not detected in testing, so any nitrite in your tank comes from the tank itself.
From EPA monitoring data (2012–2019).
Nitrate (NO₃)
5.3–6.7 ppm (Low)
Typical 6 ppm
Water changes can't take your tank's nitrate below this level.
From EPA monitoring data (2012–2019).
Copper at home taps (first draw)
0.01–0.23 ppm (Worth knowing)
The 90th percentile of first-draw samples from homes: water that sat in household pipes for at least six hours.
Shrimp and snails are sensitive to copper. Water that sits in household pipes picks up the most; it drops once the tap has run for a minute.
Published by your utility: Washington Suburban Sanitary Commission's 2025 water quality report.
Chlorine or chloramine at the tap
0–1.1 ppm
Typical 0.5 ppm
At tap levels, chlorine and chloramine are toxic to fish, shrimp and the bacteria in a filter. Water conditioners are made for this range.
Published by your utility: Washington Suburban Sanitary Commission's 2025 water quality report.
Water chemistry
General hardness
Not published yet
We haven't found this number yet. A drop test kit gives you your exact reading.
Carbonate hardness (alkalinity)
Not published yet
We haven't found this number yet. A drop test kit gives you your exact reading.
pH
Not published yet
We haven't found this number yet. A drop test kit gives you your exact reading.
- Washington Suburban Sanitary Commission adds phosphate to protect pipes. It can feed algae in tanks without much plant growth.
- Washington Suburban Sanitary Commission softens its water at the plant, so it may be softer than the local groundwater.
Who supplies Potomac, MD
- 2025 water quality report
Washington Suburban Sanitary Commission
Serves all residents · Lake or river water · Chlorine
Our data comes from public records and is still incomplete. Many utilities don't publish every number, so we're adding more all the time. Your city's range is a starting point: testing your own tap is the only way to know exactly what's in it.
Tap water lookup covers US cities only for now. Want to know why it matters? Read our story on tap water.
Compiled by Shoal & Stem from public records. Free to cite with a link.