Three distinct profiles divide the state. Northwest Indiana runs Lake Michigan supply continuous with Chicago (130-170 mg/L). Indianapolis and central Indiana run surface-water at 110-150 mg/L, with ring-suburb variance (Carmel/Westfield moderate, Boone County 160-220 mg/L). Southern Indiana karst country (Bloomington, Bedford, French Lick) runs limestone-aquifer water at 140-200 mg/L with sub-micron suspended-particulate. Evansville Ohio River-source moderate.
HOW IT BREAKS DOWNmoderate to hard (district-dependent)
Northwest Indiana Lake Michigan (130-170 mg/L) is continuous with Chicago and protocols port directly. Indianapolis surface-water moderate (110-150 mg/L). Hamilton and Boone County ring suburbs vary (130-220 mg/L). Southern Indiana karst-aquifer (140-200 mg/L) requires the same extended-dwell protocol Cal Hatcher documents for Middle Tennessee karst water. Evansville Ohio River moderate. Madison and the Ohio River corridor moderate surface-water.
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.
Indiana spans 3 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.
A distilled rinse stops being an improvement and becomes the method. Tap water left to dry on glass at this concentration deposits a visible film within minutes, and the film is cumulative: each cleaning that ends in tap water adds a layer that the next cleaning has to get through first. Glass on a sprinkler line or under a runoff drip needs a maintenance interval, not just a better wash — the deposit is arriving faster than a cleaning schedule built around dust would predict.
Hardest first — the order that matters, because the hard end is where the method has to change. Each figure is a service-area typical for the named utility. Within Indiana the spread runs from Evansville at 130 mg/L to Bloomington at 170 — a difference big enough that the same bottle of cleaner behaves differently in each.
This page is about Indiana's water and nothing else. For how cleaning actually works in Indiana across the year — climate, seasonal timing, the local contaminants, the housing stock — see the Indiana 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.
USGS national hardness survey data and utility Consumer Confidence Reports, 2023 vintage. City figures are service-area typicals for the named utility, not readings from any one tap. State ranges are the lowest and highest typical municipal values across the state, so they bracket the populated area rather than describing an average resident. Where a state blends sources seasonally, the range is wider than any single address will ever see.
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.