2025 hardness by plant
Dublin Road Water Plant, Scioto River via Griggs and O'Shaughnessy, northwest and southwest: 125 mg/L average (122–132), 7.3 grains per gallon (7.1–7.7).
Hap Cremean Water Plant, Hoover Reservoir on Big Walnut Creek, OSU and the north: 98 mg/L (85–118), 5.7 grains (5.0–6.9).
Parsons Avenue Water Plant, groundwater wells, southeast: 123 mg/L (122–127), 7.2 grains (7.1–7.4).
The report’s system summary lists hardness as CaCO3 at 115 mg/L. The city’s hardness page says Columbus softens on average to 120 ppm, about 7 grains per gallon, and describes that as moderately hard. Seventeen point one mg/L equals one grain per gallon.
Neighborhood and suburb pages on Columbus water use this system range. They do not assign a plant to a street. The city does not publish that map in a form we can cite address by address.
Columbus Water & Power says a home filter is not required to make the water safe to drink. On this supply, a softener or filter is a choice about taste, odor, scale, and how appliances wear, not a safety fix.
Other verified hardness nearby
Westerville softens at its own plant to about 125 mg/L, about 7 grains. Del-Co, which serves Powell and Sunbury, publishes about 7–8 grains (120–140 mg/L). Newark reports about 119 mg/L, about 7 grains, from the North Fork of the Licking River.
Circleville’s wells are not softened. The city says the water is hard at 25 grains per gallon. Heath softens to 145 mg/L and says home softeners are unnecessary. Delaware, Lancaster, Marysville, Pickerington, and Granville did not publish a hardness figure in the reports we reviewed.
Use this on a city page
Questions people ask
Does Columbus, Ohio have hard water?
After treatment, yes, in the moderately hard range. The city cites about 120 ppm, or 7 grains per gallon. Plant averages in 2025 were 5.7, 7.3, and 7.2 grains.
Should I use a third-party hardness map?
No. This page only uses utility reports. If a supplier did not publish hardness, the city pages say so and we test at the house.