Is Cincinnati tap water safe to drink?

Cincinnati Public Water System uses free chlorine, according to its own water quality reporting. Free chlorine is the easy case: almost any carbon filter, from a basic pitcher to a shower filter, reduces the taste and smell.

Cincinnati's water measures about 6.6 grains per gallon (113 mg/L as calcium carbonate), which is moderately hard on the US Geological Survey scale: soft below 60 mg/L, moderately hard 60-120, hard 120-180, very hard above 180.

At this level a water softener is usually not worth the cost. Spend on filtration for taste or specific contaminants instead.

Hardness data: TapWaterData Water Hardness Dataset (tapwaterdata.com), licensed CC BY 4.0. Underlying source: Utility-reported water quality data — CINCINNATI PUBLIC WATER SYSTEM (PWSID OH3102612), 2025-03-31.

In Cincinnati Public Water System's most recent lead sampling, for the period ending June 2026, 90% of tested homes came in at or below 2.1 ppb of lead. That is low on any of the federal yardsticks. The copper result for the same period was 37.60 mg/L (action level 1.3).

This is a system-wide statistic, not a reading of your tap. Lead comes from lead service lines, old solder and some brass fixtures inside homes, so two houses on the same street can differ. Testing your own tap costs $15-40, and many utilities test free on request.

EPA's lead action level is 15 parts per billion (ppb) today and drops to 10 ppb in November 2027 under the Lead and Copper Rule Improvements. FDA's limit for bottled water is 5 ppb. EPA's health goal for lead is zero.

In EPA's 2023-2025 sampling of Cincinnati Public Water System, these PFAS were detected: PFOS up to 6.1 ppt (2024 limit 4); PFBS up to 4.1 ppt (no federal limit). PFOS was measured above the 2024 limit in at least one sample. These are the highest single results; utilities are judged on running annual averages, so a high sample is not by itself a violation.

Reverse osmosis is the most reliable home treatment for PFAS. Some carbon filters are certified for PFOA and PFOS reduction under NSF/ANSI 53; check the product listing for that claim, not just the word PFAS on the box.

In April 2024 EPA set enforceable limits of 4 parts per trillion (ppt) for PFOA and PFOS, and 10 ppt for PFHxS, PFNA and HFPO-DA (GenX). In May 2025 EPA said it intends to keep the PFOA and PFOS limits, extend the compliance deadline to 2031, and rescind the other three. We compare results to the 2024 limits and label which ones may change.

Cincinnati Public Water System has no health-based violations on file with EPA since 2016.

Cincinnati is in Hamilton County, which EPA places in Radon Zone 1: the predicted average indoor level is above 4 pCi/L, EPA's action level.

In Zone 1, testing is the single highest-value home health check you can do. A $15-25 charcoal kit gives an answer in a few days; a digital monitor shows how levels move with the seasons. If you measure 4 pCi/L or more, a mitigation system (typically $800-2,500) brings it down permanently.

EPA radon zones describe counties, not houses. Zone 1 counties have a predicted average indoor level above 4 picocuries per liter (pCi/L), Zone 2 between 2 and 4, Zone 3 below 2. Homes with high levels are found in every zone, which is why EPA recommends that every home be tested, and fixed at 4 pCi/L or above. See every Ohio county's radon zone.