Ontario, CA tap water
Supplied by Ontario Municipal Utilities Company. Here's what its 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 a little ammonia. Some utilities switch to plain chlorine for a few weeks a year.
Safety for fish and shrimp
Nitrate (NO₃)
8.9–17 ppm (Worth knowing)
Typical 13 ppm
Water changes can't take your tank's nitrate below this level.
From California Water Board lab results (2023–2026).
Copper at home taps
0.07 ppm (Low)
Low. Water that sits in household pipes overnight can carry more than this.
From California Water Board lab results (2024).
Water chemistry
General hardness
Supplier's figure8–390 ppm
Typical 162 ppm
Moderately hard. Great for livebearers, and most community fish adapt.
From the utility that supplies yours: Jurupa Community SD and Water Facilities Authority-Jpa and Chino Basin Desalter Auth. - Desalter 2, which supplies Ontario Municipal Utilities Company (2023–2026).
Carbonate hardness (alkalinity)
Supplier's figure9–200 ppm
Typical 108 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From the utility that supplies yours: Jurupa Community SD and Water Facilities Authority-Jpa and Chino Basin Desalter Auth. - Desalter 2, which supplies Ontario Municipal Utilities Company (2023–2026).
pH
8.2
Alkaline. Many utilities raise pH to protect pipes. Stability matters more than the exact number.
From EPA monitoring data (2018).
Total dissolved solids
Supplier's figure27–640 ppm
Typical 305 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: Jurupa Community SD and Water Facilities Authority-Jpa and Chino Basin Desalter Auth. - Desalter 2, which supplies Ontario Municipal Utilities Company (2023–2026).
Who supplies Ontario, CA
Ontario Municipal Utilities Company
Serves 91% of residents · Buys water from Jurupa Community SD · 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.