Weldon Spring, MO tap water
Supplied mostly by Missouri American Water – St. Louis St. Charles Counties, plus 2 other utilities. Here's what the water means for your fish.
Disinfectant
Chlorine or chloramine
Utilities here use chlorine or chloramine, depending on which one serves your address. Chlorine slowly gases off from standing water; chloramine doesn't.
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)
1.8–6.3 ppm (Low)
Typical 5.7 ppm
Water changes can't take your tank's nitrate below this level.
From EPA monitoring data; St Louis City PWS, which supplies St Charles County Pwsd 2 (2012–2019).
Copper at home taps (first draw)
Up to 0.06 ppm (Low)
The 90th percentile of first-draw samples from homes: water that sat in household pipes for at least six hours.
Low. Water that sits in household pipes overnight can carry more than this.
Published by your utility: Missouri American Water – St. Louis St. Charles Counties' 2025 water quality report.
Water chemistry
General hardness
67–223 ppm
Typical 142 ppm
Moderately soft to medium. Suits most community fish and plants.
Published by your utility: Missouri American Water – St. Louis St. Charles Counties' website; St Charles County Pwsd 2's 2025 water quality report.
Carbonate hardness (alkalinity)
83–200 ppm
Typical 165 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
Published by your utility: Missouri American Water – St. Louis St. Charles Counties' 2025 water quality report; St Charles County Pwsd 2's 2025 water quality report.
pH
7.8–10.2
Typical 9.8
Alkaline. Many utilities raise pH to protect pipes. Stability matters more than the exact number.
From Missouri American Water – St. Louis St. Charles Counties' website; EPA monitoring data; St Charles County Pwsd 2's 2025 water quality report (2014–2025).
Total dissolved solids
333–410 ppm
Typical 372 ppm
A rough measure of everything dissolved in the water. RO water reads near 0, so TDS is a quick way to compare waters.
Published by your utility: St Charles County Pwsd 2's 2025 water quality report.
- Missouri American Water – St. Louis St. Charles Counties adds phosphate to protect pipes. It can feed algae in tanks without much plant growth.
- Missouri American Water – St. Louis St. Charles Counties and St Charles County Pwsd 2 soften their water at the plant, so it may be softer than the local groundwater.
Who supplies Weldon Spring, MO
- 2025 water quality report
Missouri American Water – St. Louis St. Charles Counties
Serves 73% of residents · Lake or river water · Chloramine
Weldon Spring Heights Village PWS
Serves 13% of residents · Groundwater (wells) · Chlorine
- 2025 water quality report
St Charles County Pwsd 2
Serves 12% of residents · Buys water from St Louis City PWS · 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.