San Marcos, TX tap water
Supplied mostly by City of San Marcos, plus 1 other utility. 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)
5–8.6 ppm (Low)
Typical 7.1 ppm
Water changes can't take your tank's nitrate below this level.
From EPA monitoring data (2012–2019).
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)
208–285 ppm
Typical 257 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From EPA monitoring data (2012–2019).
pH
7.3–7.8
Typical 7.7
Most community fish do well here. Stable water matters more than the exact number.
From EPA monitoring data (2012–2014).
- Texas State University - San Marcos adds phosphate to protect pipes. It can feed algae in tanks without much plant growth.
Who supplies San Marcos, TX
City of San Marcos
Serves 85% of residents · Lake or river water · Chloramine
Texas State University - San Marcos
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.