Data & Rankings
12 St. Charles County Towns Ranked by Water Hardness, 2026
Real grains per gallon (hardness) data for 12 engine/data/water towns, pulled July 2026.
How we ranked this
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The Home Water Report ranked 12 engine/data/water towns in st. charles county, sorted by grains per gallon (hardness). Every number below comes straight from the source data, not an estimate.
1. Flint Hill (St. Charles County, MO)
Grains per gallon (hardness): 16.7
If you're in Flint Hill, you're almost certainly fighting very hard water - up to 16.7 grains. That's the chalky film on your shower glass, the soap that won't lather, the crusty scale eating your faucets and shortening the life of your water heater, plus dry, itchy skin and dull, brittle hair after every shower. The...
2. Wentzville (St. Charles County, MO)
Grains per gallon (hardness): 14.0
Wentzville water is genuinely hard - 11 to 17 grains a gallon, deep in the "very hard" zone. That's the chalky white crust locking up your faucets and showerheads, the soap that won't rinse off, the filmy skin and dry, brittle hair after every shower, and scale quietly coating the inside of your water heater until it...
3. Augusta (St. Charles County, MO)
Grains per gallon (hardness): 10.8
Augusta tap is hard at about 10.8 grains and runs strongly alkaline (pH 9+), so it chalks up your faucets and showerheads with white scale, leaves spots on glasses, eats through soap, and quietly shortens the life of your water heater. It is legal water, but it carries chlorine disinfection byproducts (TTHMs) at...
4. Lake St. Louis (St. Charles County, MO)
Grains per gallon (hardness): 10.8
Your Lake St. Louis tap is a blend of Missouri River-bottom well water and purchased St. Louis river water, and it comes in hard at about 10.8 grains per gallon. That is the chalky film on your shower glass, the crusty white scale choking your faucets and shower heads, the soap that never quite rinses off your skin...
5. New Melle (St. Charles County, MO)
Grains per gallon (hardness): 10.8
If you're on New Melle city water (PWSD 2), every shower is laced with chlorine you can smell and taste, water so alkaline (pH 9+) it leaves a slick film on your skin and a chalky haze on glass, and ~11 grains of hardness that crusts faucets, fogs your shower doors, and slowly chokes your water heater with scale....
6. Portage Des Sioux (St. Charles County, MO)
Grains per gallon (hardness): 10.8
Your tap here is a blend of river-bottom well water and Missouri River water, and at ~10.8 grains it is genuinely hard - that is the chalky scale crusting your faucets, the film that won't rinse off your skin, the dull squeaky hair, and the water heater that dies years early. The pH runs at 9.13 (over the EPA's...
7. Cottleville (St. Charles County, MO)
Grains per gallon (hardness): 10.7
Cottleville tap water is hard - roughly 10 to 19 grains per gallon - and you can feel it: filmy skin that never rinses clean, dull flat hair, chalky spots on your dishes and glass shower doors, and crusty white scale building on every faucet and showerhead. That same scale is silently choking your water heater,...
8. Foristell (St. Charles County, MO)
Grains per gallon (hardness): 10.7
If you're on Foristell town water, you're showering in hard water that runs about 10.7 grains and a pH of 9.1 - above the recommended max - so it never quite rinses off. That's the slick, soapy film on your skin, the dull straw feel in your hair, and the chalky white scale crusting your faucets, glassware and...
9. Dardenne Prairie (St. Charles County, MO)
Grains per gallon (hardness): 10.0
Dardenne Prairie tap water is officially hard - about 9 to 11 grains per gallon straight from the utility's own report. That is the chalky film on your shower glass, the soap that never quite rinses off your skin, the dull film in your hair, and the white crust building up on faucets and inside your water heater (hard...
10. Defiance (St. Charles County, MO)
Grains per gallon (hardness): 10.0
Your Defiance water comes from Missouri River valley wells, and it is very hard - that's the chalky white crust building on your faucets and showerheads, the soap that never rinses off, the film on your glasses, and the reason your skin feels tight and your hair goes dry and brittle. That same scale silently coats the...
11. Weldon Spring (St. Charles County, MO)
Grains per gallon (hardness): 9.6
If you live in Weldon Spring, your tap is Missouri River water that's run through chloramine (chlorine plus ammonia) and lands at about 9.6 grains hard. You feel it everywhere: that chalky film on glass shower doors, soap that never fully rinses off skin and hair, crusty white scale choking your faucets and...
12. St. Peters (St. Charles County, MO)
Grains per gallon (hardness): 9.0
Your St. Peters tap is a blend - part Missouri River water bought from St. Louis, part well water pumped out of the Mississippi floodplain and softened by the city. Even after that softening it still runs about 8-10 grains hard, so you're getting the chalky white scale crusting your faucets and shower glass, soap that...