City of St. Peters
10.1 grains per gallon
173 mg/L. Hard.
As printed in the 2025 report.
Sodium 75.3 mg/L. Total dissolved solids 482 mg/L.
Water hardness in St. Peters, Missouri
St. Peters city water measured 10.1 grains per gallon in the city's 2025 water quality report. That is hard on the U.S. Geological Survey scale, close to the line where very hard begins.
Who supplies water in St. Peters
The City of St. Peters runs its own water system, which serves about 52,500 people.
Most city water in St. Charles County is hard or very hard
Hardness in grains per gallon, from each utility's 2025 water quality report
- Soft, 0 to 3.5
- Moderately hard, 3.5 to 7
- Hard, 7 to 10.5
- Very hard, over 10.5
- Wentzville (city wells)17.3 gpg
- O'Fallon (city system)7.2 to 16.5 gpg
- PWSD 28.3 to 10.8 gpg
- St. Peters10.1 gpg
- St. Charles (city)8.9 gpg
- Missouri American Waterabout 5 to 7 gpg calculated
What that means at home
At this hardness, scale builds up in water heaters and on fixtures, and soap does not lather well. None of that is a health risk. It is wear on the house and more cleaning.
What we would look at
A test at your tap comes first. It tells us your real hardness and whether your water carries chlorine or chloramine. From there, the usual options are a water softener for scale, a carbon filter for taste and smell, and reverse osmosis for drinking water. Sometimes the answer is none of them.
Common questions
How hard is the water in St. Peters?
St. Peters city water measured 10.1 grains per gallon in the city's 2025 water quality report. That is hard on the U.S. Geological Survey scale, close to the line where very hard begins.
Who provides water in St. Peters?
The City of St. Peters runs its own water system, which serves about 52,500 people.
Do you serve St. Peters?
Yes. We are based in Wentzville and serve homes on city water across St. Charles County.
Figures for St. Peters are from City of St. Peters 2025 water quality report, as published on the Missouri Department of Natural Resources website, read on October 27, 2026. Most hardness results are 2023 samples reprinted in the 2025 reports. Last reviewed November 10, 2026.
Find out how hard your water is.
The test is free, it takes place at your kitchen sink, and you see the numbers yourself.