Public Water Supply District 2 of St. Charles County (PWSD 2)
8.3 to 10.8 grains per gallon
142 to 184 mg/L. Hard to very hard.
Range across the district's sources.
Serves about 100,000 people. It also sells water to Wentzville and O'Fallon.
Water hardness in Lake Saint Louis, Missouri
Most of Lake Saint Louis gets its water from PWSD 2, which reports hardness of 8.3 to 10.8 grains per gallon in its 2025 water quality report. That is hard to very hard on the U.S. Geological Survey scale. Your water bill names your provider.
Who supplies water in Lake Saint Louis
Lake Saint Louis does not run its own water system. The city's map of water providers shows PWSD 2 serving nearly all of the city, and the City of O'Fallon and the City of Wentzville serving a few small areas. Your water bill names your provider.
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
Sources: PWSD 2 2025 water quality report.
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 Lake Saint Louis?
Most of Lake Saint Louis gets its water from PWSD 2, which reports hardness of 8.3 to 10.8 grains per gallon in its 2025 water quality report. That is hard to very hard on the U.S. Geological Survey scale. Your water bill names your provider.
Who provides water in Lake Saint Louis?
Lake Saint Louis does not run its own water system. The city's map of water providers shows PWSD 2 serving nearly all of the city, and the City of O'Fallon and the City of Wentzville serving a few small areas. Your water bill names your provider.
Do you serve Lake Saint Louis?
Yes. We are based in Wentzville and serve homes on city water across St. Charles County.
Figures for Lake Saint Louis are from PWSD 2 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.