Onset, MA tap water
Supplied mostly by Onset Fire Districtwater Dept., plus 1 other utility. Here's what the water means for your fish.
Disinfectant
Not confirmed
We couldn't confirm how your water is disinfected. US utilities use chlorine or chloramine, and chloramine doesn't gas off when water sits out.
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 (2012–2018).
Nitrate (NO₃)
Up to 1.8 ppm (Low)
Typical 1.3 ppm
Low, so water changes lower your tank's nitrate well.
From EPA monitoring data (2012–2019).
Water chemistry
General hardness
Area estimate10–41 ppm
Typical 26 ppm
Soft. Good for tetras, rasboras and most shrimp. Livebearers, snails and African cichlids prefer harder water.
Area estimate from nearby wells: USGS well samples in your county (2000–2019).
Carbonate hardness (alkalinity)
Area estimate2–77 ppm
Typical 12 ppm
Little buffering. pH can drop quickly between water changes, especially with CO₂ or an older tank.
Area estimate from nearby wells: USGS well samples in your county (2000–2019).
pH
6.8–9.6
Typical 8
Most community fish do well here. Stable water matters more than the exact number.
From EPA monitoring data (2012–2019).
Total dissolved solids
Area estimate46–281 ppm
Typical 82 ppm
A rough measure of everything dissolved in the water. RO water reads near 0, so TDS is a quick way to compare waters.
Area estimate from nearby wells: USGS well samples in your county (2000–2019).
Who supplies Onset, MA
Onset Fire Districtwater Dept.
Serves all residents · Groundwater (wells) · Disinfectant not listed
Wareham Fire District
Serves 7% of residents · Groundwater (wells) · 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.