Welby, CO tap water
Supplied mostly by North Washington Street WSD, 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 0.63 ppm of ammonia here. Some utilities switch to plain chlorine for a few weeks a year.
Safety for fish and shrimp
Ammonia (with conditioner)
Estimate0.19–0.95 ppm (Worth knowing)
Typical 0.63 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 City of Thornton reports (2025).
Nitrite (NO₂)
Up to 0.26 ppm (Worth knowing)
Typical 0.26 ppm
Some nitrite shows up in this tap water, which can happen in chloramine systems, and it goes into the tank with each water change.
Published by your utility: City of Thornton's 2025 water quality report.
Nitrate (NO₃)
Supplier's figure0.3–3.5 ppm (Low)
Typical 0.4 ppm
Low, so water changes lower your tank's nitrate well.
From the utility that supplies yours: Denver Water Board, which supplies North Washington Street WSD; City of Thornton's 2025 water quality report.
Copper at home taps (first draw)
0.47 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: City of Thornton's 2025 water quality report.
Chlorine or chloramine at the tap
0.8–3.9 ppm
Typical 2.6 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: City of Thornton's 2025 water quality report.
Water chemistry
General hardness
Supplier's figure55–356 ppm
Typical 105 ppm
Moderately soft to medium. Suits most community fish and plants.
From the utility that supplies yours: Denver Water Board, which supplies North Washington Street WSD; City of Thornton's 2025 water quality report.
Carbonate hardness (alkalinity)
Supplier's figure41–112 ppm
Typical 65 ppm
Moderate buffering. pH should stay fairly steady.
From the utility that supplies yours: Denver Water Board, which supplies North Washington Street WSD; EPA monitoring data (2014–2025).
pH
7.4–9
Typical 8.1
Alkaline. Many utilities raise pH to protect pipes. Stability matters more than the exact number.
Published by your utility: City of Thornton's 2025 water quality report.
Total dissolved solids
Supplier's figure98–679 ppm
Typical 220 ppm
A rough measure of everything dissolved in the water. RO water reads near 0, so TDS is a quick way to compare waters.
From the utility that supplies yours: Denver Water Board, which supplies North Washington Street WSD; City of Thornton's 2025 water quality report.
- North Washington Street WSD and City of Thornton add phosphate to protect pipes. It can feed algae in tanks without much plant growth.
Who supplies Welby, CO
North Washington Street WSD
Serves 85% of residents · Buys water from Denver Water Board · Chloramine
- 2025 water quality report
City of Thornton
Serves 8% 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.