Kentucky splits into five chemistry zones. Louisville runs Louisville Water Company Ohio River-source. Lexington runs Kentucky-American Kentucky River. Bluegrass horse-country wells (Woodford, Bourbon, Scott, Jessamine) run karst. Cave country wells (Bowling Green, Mammoth Cave region) run karst. Northern Kentucky runs Ohio River continuous with Cincinnati. Eastern Kentucky carries its own coalfield-heritage exposure profile.
HOW IT BREAKS DOWNhard (Lexington, Bowling Green, Louisville, Covington); 1 of 5 covered cities publishes no figure
Louisville and Northern Kentucky protocols port from Cincinnati. Lexington proper publishes hard. Bluegrass horse-country requires extended karst-protocol citric dwell (3-4 minutes). Cave country requires the same extended protocol. Eastern Kentucky residential needs heavy-industrial-exposure protocol on coalfield-heritage stock from historical coal-burning aerial deposition. Five protocol zones — do not run a single Kentucky protocol.
A blended system means hardness moves with the blend. Two addresses on the same utility can read differently, and the same address can read differently across a year, depending on which source is carrying the load that season.
Kentucky spans 2 hardness bands, which means there is no single answer for the whole state — the method changes as you move across it. Both ends are below.
Tap water is still fine for most residential glass, with two exceptions worth knowing. Dark glass shows a faint mineral haze that lighter glass hides, and glass that is hot enough to flash the water off before you pull the squeegee will spot regardless of how soft the supply is. On both, a distilled final rinse costs about a dollar a window and removes the variable entirely. Everywhere else at this level, the water is not what is wrong.
This is the band where the water starts writing on the glass. Wash with tap — the surfactant holds the minerals in suspension while you work, so the wash pass is not the problem — then rinse with distilled and pull that. The rinse is the whole intervention: it replaces the mineral-bearing water sitting on the glass with water that has nothing in it to leave. This single change resolves most of the "I cleaned it and it still looks bad" complaints in this range, and it does not require buying a system.
Hardest first — the order that matters, because the hard end is where the method has to change. Each figure is the named utility's own published number; cities whose utility publishes none are listed after them, without a band. Within Kentucky the spread runs from Covington at 88–156 mg/L to Lexington at 149–161 mg/L — a difference big enough that the same bottle of cleaner behaves differently in each.
Where Kentucky's city pages sit in the national city rankings: hardness rank out of 185 cities whose utility publishes a figure, dissolved-solids rank out of 100, the disinfectant each utility reports, and the months each city's cleaning calendar marks for a wash. Rank 1 is the hardest or most mineral-heavy. 2 of these 5 cities use chloramine.
| CITY | HARDNESS RANK | TDS RANK | DISINFECTANT | WASH IN |
|---|---|---|---|---|
| Lexington | 44 / 185149–161 mg/L | 41 / 100168–304 mg/L | chloramine | Jul, Oct |
| Bowling Green | 50 / 185150 mg/L | not ranked | free chlorine | Jun, Oct |
| Louisville | 78 / 185128 mg/L | 42 / 100225 mg/L | chloramine | Jul, Oct |
| Covington | 86 / 18588–156 mg/L | 49 / 100107–263 mg/L | uv + chlorine | Aug, Oct |
| Owensboro | not ranked | not ranked | free chlorine | Jul, Oct |
This page is about Kentucky's water and nothing else. For how cleaning actually works in Kentucky across the year — climate, seasonal timing, the local contaminants, the housing stock — see the Kentucky cleaning guide.
For a figure at your own address rather than your city, the Hard Water Scorer takes a ZIP code. If you run a pure-water system, the TDS diagnostic reads the other end of the same problem.
Each covered city utility's own published figure, taken from its most recent annual water quality report (Consumer Confidence Report) or its water-quality page, read in 2026. A city figure is the one its utility publishes for the service area, as a single number or the range it reports; it is not a reading from any one tap. A state range runs from the lowest to the highest figure published by the utilities we cover in that state, so it brackets those cities rather than describing an average resident. A state where no covered utility publishes a figure shows a planning estimate, labelled as one.
Private wells are outside all of it. A well is whatever the rock under it says, and the only number that describes one is a test of that tap. Have a reading that disagrees with this table? Send it to us — a number that contradicts the table is worth more than one that confirms it.