Our service area page answers the question "do you come out this far?" This page answers a harder one: what is actually coming out of the tap in your town, and what does it take to fix it? Water does not change at a county line. It changes street by street, well by well, and by which utility bought which source that year.
Below is every community we serve, grouped by county, with the real hardness number we have on file for it. Where we keep a dedicated local water guide for a town or a specific problem, it is linked in the write-up for that county.
How to read these numbers
Where the data comes from: Jones Air & Water's own 57-town water hardness dataset, built from utility consumer confidence reports, Missouri DNR and EPA well data, and our own in-home testing across St. Charles, St. Louis, Jefferson, Lincoln, Warren and Franklin counties in Missouri and Madison, Jersey and St. Clair counties in Illinois. Pulled in 2026. The sort criterion inside each county table is grains per gallon (gpg), low to high. Every number below is the number in that file, not an estimate we made up for the page.
What the grade means: A and B are water most homes can live with. C is hard: you will see spotting and your water heater will run less efficiently. D is very hard. F is extremely hard, which in this region usually means limestone and dolomite bedrock, and it is where softener sizing stops being optional. The annual cost column is the yearly hard-water cost we associate with that grade band across the dataset (soap and detergent waste, water heating losses, and shortened appliance life). It is a band, not a bill.
One caveat we will repeat all the way down this page: a city number describes the treated municipal supply. If you are on a private well, the city number next to your town is not your water. Private wells in this region routinely run 15 to 25+ gpg with iron and sulfur on top. That is why we test at your sink instead of quoting off a chart.
St. Charles County
| Town | Hardness (gpg) | Grade | Annual hard-water cost band |
|---|---|---|---|
| O'Fallon | 8.0 | C | $600 |
| St. Charles | 8.9 | C | $600 |
| St. Peters | 9.0 | C | $600 |
| Weldon Spring | 9.6 | C | $600 |
| Dardenne Prairie | 10.0 | D | $900 |
| Defiance | 10.0 | D | $900 |
| Cottleville | 10.7 | D | $900 |
| Foristell | 10.7 | D | $900 |
| Augusta | 10.8 | D | $900 |
| Lake St. Louis | 10.8 | D | $900 |
| New Melle | 10.8 | D | $900 |
| Portage Des Sioux | 10.8 | D | $900 |
| Wentzville | 14.0 | D | $900 |
| Flint Hill | 16.7 | F | $1,150 |
This is home. Our shop is in Portage Des Sioux and most of our work happens inside these fourteen towns.
The city of St. Charles runs about 8.9 gpg, which sounds tame until you look at the rest of the report: pH measured at 9.36 on the city side and 9.69 on the St. Louis side, both well over the 8.5 secondary limit, which is why the water can feel slick and leave that chalky ring. That combination is exactly what we walk people through in our guide to hard water in St. Charles, and it is the reason water softeners for St. Charles homes get sized on more than one number. If your house was built before the lead service line inventory started, the plumbing itself is part of the picture, and a lab panel matters more than a hardness strip: that is the case for testing St. Charles tap water properly. When the fix has to go past softening, into taste, chlorine byproducts and sediment, we cover it under whole-house filtration in St. Charles.
Step outside the city mains and the county splits in two. Portage Des Sioux, Augusta, Defiance, Foristell and the Femme Osage bottoms sit on Missouri River alluvial aquifer wells where iron, manganese and sulfate routinely exceed the secondary limits and the rotten-egg smell is a weekly phone call for us. Nothing on the municipal side of this table describes that water, which is why well water in St. Charles County gets its own guide. Flint Hill is the other end: 16.7 gpg on the village supply, radium at 2.5 pCi/L and gross alpha at 7 pCi/L, versus 10.8 gpg on PWSD #2 water a few minutes away. Same zip code, different water. Sizing across that spread is the whole subject of softener sizing across St. Charles County.
O'Fallon reads 8.0 gpg treated, but the raw county and well water behind it runs closer to 15 to 20 gpg, and combined radium sits between 2.0 and 3.3 pCi/L. We break that gap down in our guides to water treatment in O'Fallon and, for homeowners who already know softening is the answer, O'Fallon water softeners. St. Peters comes in at 9.0 gpg after the city's own softening, with chloride at 138 mg/L and sodium at 75 mg/L, a profile that changes what we recommend for drinking water: see water softeners in St. Peters. Lake St. Louis is a 10.8 gpg D with purchased water measured as high as 9.69 pH, and the ring of private wells around the lake runs harder still, which is where the Lake St. Louis softener guide starts.
Wentzville is the town in this county we get called about most, and the table shows why: 14.0 gpg, an 11 to 17 gpg range depending on which well is running, and combined radium at 4 pCi/L, which is 80 percent of the federal limit. Two very different private-well profiles ring the city, shallow river-bottom wells heavy in iron and sulfur and deep bedrock wells heavy in hardness and radium. Read water softeners in Wentzville for the treatment side, and Wentzville water testing for figuring out which of those two profiles you actually have before you buy anything.
Lincoln County
| Town | Hardness (gpg) | Grade | Annual hard-water cost band |
|---|---|---|---|
| Elsberry | 13.0 | D | $900 |
| Moscow Mills | 16.0 | F | $1,150 |
| Hawk Point | 16.1 | F | $1,150 |
| Silex | 17.0 | F | $1,150 |
| Old Monroe | 18.3 | F | $1,150 |
| Winfield | 18.3 | F | $1,150 |
| Troy | 19.2 | F | $1,150 |
| Foley | 20.0 | F | $1,150 |
Seven of Lincoln County's eight towns in our dataset grade F. This is the hardest stretch of our Missouri coverage, and it is not a treatment failure, it is geology: limestone and dolomite under most of the county.
Troy is the anchor at 19.2 gpg, with naturally occurring fluoride at 2.59 ppm (above the 2.0 ppm dental fluorosis warning level), TDS at 668 ppm and sodium at 124 ppm. A standard 32,000-grain softener sized off a St. Louis brochure will run out of capacity in a Troy house, and it will do it in the middle of a shower. That is the practical starting point for water treatment in Troy, Missouri. Silex is worth naming too: we wrote up the actual EPA radium numbers behind Silex's bottled water order and the neighboring towns, because radium is the one thing here that a softener does help with and most homeowners never think to ask about.
Warren County
| Town | Hardness (gpg) | Grade | Annual hard-water cost band |
|---|---|---|---|
| Innsbrook | 10.8 | D | $900 |
| Wright City | 10.8 | D | $900 |
| Truesdale | 14.5 | D | $900 |
| Warrenton | 16.0 | F | $1,150 |
| Marthasville | 20.0 | F | $1,150 |
Warrenton does not soften its water, and it does not pretend to: 16.0 gpg, 274 ppm, straight to the tap, plus TDS at 502 mg/L just over the EPA secondary limit and combined radium-226/228 around 2.06 to 2.9 pCi/L. Homeowners here are doing the softening themselves or they are replacing water heaters early. Our county write-up on water treatment in Warrenton, MO covers what that means for sizing and for the private wells around Marthasville and Innsbrook, which are unregulated, untested by anyone, and typically harder than the town supply.
Franklin County
| Town | Hardness (gpg) | Grade | Annual hard-water cost band |
|---|---|---|---|
| Sullivan | 13.3 | D | $900 |
| St. Clair | 14.6 | D | $900 |
| Washington | 16.5 | F | $1,150 |
| Union | 17.5 | F | $1,150 |
| Gerald | 17.8 | F | $1,150 |
| Labadie | 18.0 | F | $1,150 |
| Villa Ridge | 18.1 | F | $1,150 |
| New Haven | 18.5 | F | $1,150 |
| Pacific | 19.3 | F | $1,150 |
Washington is one of a handful of towns in this dataset where the city's own report shows iron over the guideline before the water ever reaches your house: 0.43 mg/L against a 0.30 mg/L secondary limit, on top of 16.5 gpg hardness, combined radium at 1.9 pCi/L and gross alpha at 7.3 pCi/L. Gerald is worse on that one measure at 0.73 mg/L, and Pacific and Truesdale sit right at the line. Iron over the guideline is orange staining you cannot scrub out of a toilet, and a softener alone is the wrong tool for it. We lay out the order of operations in water treatment for Washington, MO. On the private wells south and west of town, iron commonly runs 1 to 10 mg/L, three to thirty-three times the guideline, which moves the conversation to dedicated iron filtration.
Jefferson County
| Town | Hardness (gpg) | Grade | Annual hard-water cost band |
|---|---|---|---|
| Festus | 5.3 | B | $250 |
| Herculaneum | 5.5 | B | $250 |
| High Ridge | 5.7 | B | $250 |
| Arnold | 8.0 | C | $600 |
| Barnhart | 8.5 | C | $600 |
| Imperial | 8.5 | C | $600 |
| Byrnes Mill | 15.0 | F | $1,150 |
| Cedar Hill | 18.0 | F | $1,150 |
| Hillsboro | 19.0 | F | $1,150 |
| Pevely | 19.0 | F | $1,150 |
| House Springs | 19.4 | F | $1,150 |
| Crystal City | 19.5 | F | $1,150 |
| De Soto | 21.0 | F | $1,150 |
Jefferson County has the widest spread of any county we serve: 5.3 gpg in Festus and 21.0 gpg in De Soto, less than twenty miles apart. The northern river towns buy treated water. The interior towns, Cedar Hill, House Springs, Hillsboro, Byrnes Mill, sit on the Ozark limestone and dolomite aquifer, and they show it.
Arnold is the interesting case, because 8.0 gpg is genuinely middling hardness and the hardness is not the headline. The chemistry is: chloramine instead of chlorine (harder to filter and it will not gas off in a pitcher), TTHMs at 47 ppb, HAA5 at 29 ppb, and chromium-6 at 1.3 ppb. A softener does not touch any of those. Our guide to water treatment in Arnold is mostly about carbon and reverse osmosis for that reason, with softening as the appliance-protection layer underneath.
Illinois: Madison and Jersey counties
| Town | County | Hardness (gpg) | Grade |
|---|---|---|---|
| Godfrey | Madison | 8.5 | C |
| Bethalto | Madison | 13.5 | D |
| Alton | Madison | 14.0 | D |
| Granite City | Madison | 14.5 | D |
| Grafton | Jersey | 15.0 | F |
| Jerseyville | Jersey | 21.5 | F |
| Edwardsville | Madison | 24.0 | F |
| Wood River | Madison | 24.5 | F |
Edwardsville at 24.0 gpg and Wood River at 24.5 gpg are the two hardest municipal supplies in our entire dataset, harder than most private wells we test in Missouri. Illinois also does not routinely test private wells, so owners in the American Bottoms river-bottom country, where we have seen iron reported as high as 82,000 ug/L, are genuinely on their own. We cross the river for this work; there is no separate guide site for the Illinois side yet, so call us or use the water quality map for your address.
St. Louis City and County
St. Louis is not a single water. City water measures roughly 7.8 to 12.8 gpg depending on the area and the source, which we go through in well water vs. city water in St. Louis. It is treated Mississippi and Missouri River water, so the hardness swings with the river and the season, and the problems people call us about in the metro tend to sort into four buckets rather than one.
Scale, spotting and dead water heaters, which is the classic hard water in St. Louis complaint. Not knowing what is in it, which is where St. Louis water testing comes in, and it matters more here than in a small town because the source blend changes. Orange staining and metallic taste, almost always from a well or from older galvanized plumbing, covered under iron water removal in St. Louis. And salt: plenty of metro homeowners want the scale protection without a brine tank or a softened-water sodium bump, which is the case for salt-free water systems in St. Louis. Everett's honest installer take on when salt-free is and is not the right call is on the blog.
The fifth St. Louis problem is not water at all. Humidity in this region sits high enough that basements and crawl spaces stay damp through the summer, and the musty smell that follows a rain is a moisture problem, not an air freshener problem. That is the subject of whole-house dehumidifiers in St. Louis.
Private wells across Missouri
A large share of the homes we work in are on a private well, and none of the numbers in the tables above apply to them. Missouri does not regulate or routinely test private wells; the state lab checks nitrate and fluoride and nothing else. Across the well profiles in our dataset the pattern is consistent enough to predict: 15 to 25+ gpg hardness on limestone and dolomite, iron and manganese staining in the river-bottom alluvium, hydrogen sulfide rotten-egg odor from deeper bedrock, nitrate wherever row crops or septic fields are close, and bacteria in anything shallow or old. Missouri surveys have found total coliform in 56 percent of private wells and E. coli in 22 percent.
That is the argument for testing before buying equipment, every time, and it is why we keep a separate guide to well water testing in Missouri. What thirty years of running both kinds of samples taught us is in well water vs. city water: 30 years of testing.
Air, not just water
A good part of what we install is air: whole-house purification, UV germicidal lights, humidifiers and dehumidifiers. In St. Charles the same houses that fight hard water fight winter dryness and summer damp, on the same air handler, which is why we treat the two as one system. Our local write-up is air purification in St. Charles, and the product side lives on our air products page.
Do not see your town?
The dataset is 57 towns and the truck goes about 75 miles in every direction from St. Charles, so the map is wider than the list. Type your town into the Check Your Water tool for an instant report card, look up your exact address on the water quality map, or just call and ask. Everett or Austin will pick up.