O'Fallon, IL tap water
Supplied mostly by O Fallon, plus 1 other utility. Here's what the water means for your fish.
Disinfectant
Chloramine
Your water is treated with chloramine. Unlike chlorine, it doesn't gas off when water sits out, and many pitcher and fridge filters aren't rated to remove it. Conditioners that list chloramine on the label break it apart, which frees about 0.61 ppm of ammonia here. Some utilities switch to plain chlorine for a few weeks a year.
Safety for fish and shrimp
Ammonia (with conditioner)
Estimate0.49–0.73 ppm (Worth knowing)
Typical 0.61 ppm
This is what a conditioner frees when it breaks the chloramine apart. A cycled filter clears it within a day; a big water change in a new or very small tank adds more of it at once. Some conditioners also bind ammonia for a day or so.
Estimated from the chloramine level Illinois American Water - East St Louis reports (2025).
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)
Supplier's figure8.9–12 ppm (Low)
Typical 8.9 ppm
Water changes can't take your tank's nitrate below this level.
From the utility that supplies yours: Illinois American Water – East St. Louis, which supplies O Fallon; Illinois American Water - East St Louis' 2025 water quality report.
Copper at home taps (first draw)
0.21 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: Illinois American Water - East St Louis' 2025 water quality report.
Chlorine or chloramine at the tap
2–3 ppm
Typical 2.5 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: Illinois American Water - East St Louis' 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)
Supplier's figure142–147 ppm
Typical 145 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From the utility that supplies yours: Illinois American Water – East St. Louis, which supplies O Fallon; EPA monitoring data (2017–2019).
pH
Not published yet
We haven't found this number yet. A drop test kit gives you your exact reading.
- O Fallon and Illinois American Water - East St Louis add phosphate to protect pipes. It can feed algae in tanks without much plant growth.
Who supplies O'Fallon, IL
O Fallon
Serves 89% of residents · Buys water from Illinois American Water – East St. Louis · Chloramine
- 2025 water quality report
Illinois American Water - East St Louis
Serves 11% of residents · Lake or river water · Chloramine
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.