Is Cincinnati Tap Water Safe to Drink? An Honest Answer

Is Cincinnati tap water safe to drink?

Yes. Cincinnati tap water is safe to drink. Greater Cincinnati Water Works reported no violations of any federal or state drinking water standard in its 2025 Water Quality Report, and the report states that GCWW water meets or exceeds every health standard set by the US EPA and Ohio EPA.

We install water treatment equipment for a living, so it would be easy for us to tell you the tap water here is a problem. It is not. If you are on GCWW water and you like how it tastes, you can stop reading. What follows is what the utility does well, and the shorter list of things no municipal plant is built to handle.

What Greater Cincinnati Water Works does well

At the Richard Miller Treatment Plant on the Ohio River, GCWW runs coagulation, flocculation and sedimentation, then sand filtration, granular activated carbon, ultraviolet light, and chlorine. GCWW says in its 2025 report that it is one of the first in the nation to use a combination of all of these methods.

Three of those deserve attention.

**Granular activated carbon.** GCWW says Miller is one of only a few plants in the nation that uses GAC with on site reactivation. Carbon adsorbs organic chemicals, industrial contaminants, and the compounds that cause taste and odor. GCWW lists a barrier against chemical spills in the Ohio River among the benefits, and says GAC means less chlorine is required for disinfection.

**Ultraviolet disinfection.** GCWW says it is the largest water utility in North America to use UV disinfection following rapid sand filtration and GAC. UV is what protects against Cryptosporidium, which chlorine does not reliably kill. In 2025 GCWW detected Cryptosporidium in 1 of 4 Ohio River source water samples and did not detect it in its finished water.

**Chlorine, not chloramine.** GCWW's published treatment diagrams for both plants show chlorine added with no ammonia step, and chloramine does not appear anywhere in the 2025 report. This matters more than most people realize. Chloramine is harder to remove, harder on rubber plumbing gaskets, and it is the reason home filters in chloraminated cities need far more carbon contact time. Chlorine without an ammonia step dissipates on its own and a standard carbon filter strips it easily.

Miller supplies about 88 percent of GCWW's drinking water. The Charles M. Bolton plant, drawing groundwater from 13 wells in the Great Miami Buried Valley Aquifer, supplies the other 12 percent, and it runs a different and simpler process: GCWW's diagram for Bolton shows lime softening, then chlorine and fluoride, then coal and sand filtration, with no carbon or UV step. Across both plants GCWW treats about 120 million gallons a day and runs more than 600 daily tests.

What the 2025 test results actually show

The numbers are good, and a few are worth knowing.

**Lead.** GCWW reports no detectable lead in the water as it leaves the treatment plants, and it runs corrosion control specifically to keep lead from leaching out of home plumbing. In 2025 the 90th percentile results were 1.32 ppb and 1.92 ppb against a 15 ppb action level. Zero of 113 samples in the first compliance period and zero of 108 in the second exceeded it.

**Disinfection byproducts.** Total trihalomethanes came in at a highest compliance level detected of 49.6 ppb against a limit of 80, with individual results ranging from 15.7 to 76.0 ppb. That is compliant, and it is the closest to its limit of any currently enforceable standard in the report. Haloacetic acids came in at 12.6 ppb against a limit of 60. Both figures are the report's compliance numbers, not the average of every sample.

Fluoride came in at 0.88 ppm at Miller and 0.86 ppm at Bolton. Sodium measured 31 mg/L at Miller and 32 mg/L at Bolton.

What water treatment does not remove

Municipal treatment is built to make water safe, not to make it soft or to make it taste like anything in particular. Three things survive it.

**Hardness.** Miller does not soften. Its water averages 126 mg/L, which works out to about 7.4 grains per gallon. On the Water Quality Association scale, soft is 0 to 3.5 grains, moderate is 3.5 to 7, hard is 7 to 10.5, and very hard is anything above 10.5. So Miller water is hard. Bolton is lime softened at the plant and still comes out at 140 mg/L, about 8.2 grains per gallon. GCWW says plainly in its own report that hardness does not affect the safety of water. It is a scale, soap, and appliance issue.

**PFAS, depending on which plant serves you.** This is where the two plants diverge. At Miller, PFOA, PFOS and PFHxS were all non detect in 2025. The one PFAS compound that did show up at Miller is GenX, at a 0.7 ppt average and a range of non detect to 3.5 ppt, against the 10 ppt limit the 2024 federal rule set for it. At Bolton, PFOA averaged 5.0 ppt and PFOS averaged 5.2 ppt, both above the 4.0 ppt limits EPA finalized in April 2024.

GCWW is not in violation today. Those limits carry a compliance deadline of 26 April 2029. In May 2026 EPA announced it would keep the 4.0 ppt limits and proposed a separate rule that would let a system request a two year extension to 26 April 2031. That extension would be opt in, not automatic, and it is still a proposal. A nearer date is already fixed: GCWW's 2025 report notes that under the 2024 rule, initial finished drinking water PFAS monitoring is required by April 2027.

**Whatever is in your own plumbing.** GCWW owns the service line from the water main to the property line. The property owner owns the line from the property line to the meter. Before you assume a lead line is yours to pay for, check the map. GCWW's lead service line replacement program covers lines on both the public and private side, and GCWW states there is no cost to the property owner because it covers the full replacement cost. The lead service line lookup map is at lead.myGCWW.org.

How hard is water in the Cincinnati area?

GCWW sits in the hard band, and most systems around it run harder.

In the metro:

- Northern Kentucky Water District: about 7.3 gpg on average, ranging 4.6 to 9.8 across the year - Greater Cincinnati Water Works: 7.4 gpg (Miller), 8.2 gpg (Bolton) - City of Hamilton: 7.6 gpg - Butler County Water and City of Fairfield: 7.7 gpg - Warren County: 8 gpg - City of Harrison: 8 gpg, down from 21 gpg before its reverse osmosis softening plant was fully activated on 3 October 2022 - Indian Hill: 8.8 to 9.9 gpg - City of Wyoming: 10.1 gpg

Farther out, past the immediate metro:

- Dayton, Kettering and Centerville: 8.1 gpg - Greene County: 8 gpg, down from 27 gpg before its reverse osmosis plant phased in through March 2024 - Oxford: 20 to 22 gpg - Aurora, Indiana: 21.05 gpg - Xenia: 23 gpg

Northern Kentucky Water District is the one nearby system that runs about level with GCWW or slightly softer, and its number swings a good deal with the season. A number of area systems, including Middletown, Springboro, Trenton, Loveland, and Lawrenceburg and Batesville in Indiana, do not publish a hardness figure at all.

GCWW as a utility serves Cincinnati, Blue Ash, Montgomery, Kenwood, Sharonville, Springdale, Forest Park and Anderson Township. Its 2025 report describes the service area as the entire City of Cincinnati, most of Hamilton County, parts of Butler and Warren Counties in Ohio, and Boone County in Kentucky. GCWW does not publish which of its two plants serves which address, so anyone who tells you your street is on Miller or on Bolton is guessing. GCWW is the one place to ask, at 513.591.7700. A footnote in the 2025 report adds that Ohio EPA treated Miller and Bolton as one distribution system for regulatory purposes during 2025, and that the data listed for each system represents the combined distribution system.

So should you filter Cincinnati tap water?

Filter for taste, hardness, and PFAS. Not for safety.

Here is the honest split. On Miller water, PFOA, PFOS and PFHxS are all non detect, and the one PFAS that does show up sits at 0.7 ppt against a 10 ppt limit. Softening is a comfort and appliance decision: less scale in the water heater, less soap, longer fixture life. Carbon at the tap takes out the chlorine taste. Neither one is urgent.

The PFAS case is different if you are on Bolton water, or on one of the southwest Ohio systems currently testing above 4.0 ppt for PFOA or PFOS. Those include GCWW's Bolton plant (PFOA 5.0, PFOS 5.2), Indian Hill (PFOS 11.7), the City of Hamilton's South plant (PFOA 5.30), Clermont County's MGS plant, which serves Miami, Goshen and Stonelick townships (PFOS 9.22 to 10.9), Wilmington (PFOS 8.79), and Dayton's Ottawa plant (PFOS 8.81). Reverse osmosis is the treatment that removes PFAS. If you are on one of those systems, putting RO in at the kitchen sink now is a reasonable call rather than waiting on a compliance deadline that may still move.

Lead is the one thing on this list you should not buy equipment for first. Check lead.myGCWW.org to see whether your property is in the replacement program. Where GCWW replaces a line, it covers the full cost.

What we install

Our Complete Home System is $3,492, flat rate, with installation included on garage, basement and utility closet installs. That covers whole house softening plus reverse osmosis drinking water at the kitchen tap. The tank carries a lifetime warranty and the valve is covered for five years. Annual RO filter changes are $199.

If you want to talk through what is actually in your water and what, if anything, you need, call us at (513) 466-0716. If the answer is that you do not need anything, we will tell you that too.