Water hardness in Cincinnati
7.8 gpg hard
Tap water in Cincinnati is hard: 7.8 gpg (133 mg/L · 7.5 °dH · 13.3 °fH).
Source: Greater Cincinnati Water Works 2025 Water Quality Report (2025) · data checked 2026-10-19
Range across supply zones: 126–140 mg/L.
2 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| gpg | mg/L | ||
|---|---|---|---|
| Charles M. Bolton plant (Great Miami Buried Valley Aquifer) | 8.2 | 140 | hard |
| Richard Miller plant (Ohio River surface water) | 7.4 | 126 | hard |
Greater Cincinnati Water Works runs two plants. The Richard Miller plant treats Ohio River water and averages 126 mg/L (7 gpg), and the Charles M. Bolton plant draws on the Great Miami Buried Valley Aquifer at 140 mg/L (8 gpg) in the 2025 report. The page shows 133 mg/L (7.8 gpg), the median of the two. Both are hard, so scale is likely whichever plant serves you.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 7.8 gpg |
|---|---|
| Utility | Greater Cincinnati Water Works (GCWW) |
How Cincinnati compares
- Tap water in Cincinnati is 14 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 815 of 1372 in the United States (1 = hardest); 40 % of these cities have softer water.
- In Ohio it is number 5 of 31 cities; the regional median is 7 gpg.
- Nearest city with clearly harder water: Richmond, 87 km away (17.1 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Fast scale on taps, shower screens and kettle; white spots on glassware.
- Water heater: efficiency loss and element failures within years if unprotected.
- Dry skin and dull hair after showering are common.
- Softener recommended; jug or reverse osmosis for drinking.
How much salt will you use for softening?
Recommended, especially with a heater or boiler: scale cuts efficiency and shortens its life.
Descale a coffee machine or kettle about every 2 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Cincinnati
| Brand | Setting for this water |
|---|---|
| Bosch | H01 |
| Miele | 7 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| LG | H2 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Cincinnati water hard or soft?
It is hard: 133 mg/L as CaCO₃ (7.8 gpg, 7.5 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Cincinnati safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
How many grains per gallon is Cincinnati water?
7.8 gpg, equal to 7.5 °dH, 13.3 °fH or 133 mg/L calcium carbonate.
What dishwasher salt setting should I use in Cincinnati?
For 133 mg/L (7.5 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Cincinnati?
Recommended if you have a water heater, boiler or tankless unit: it saves repairs and detergent.
Source
Source: Greater Cincinnati Water Works 2025 Water Quality Report (2025). Method: figure published by the water supplier. Greater Cincinnati Water Works 2025 Water Quality Report · Outdated figure? Tell us