Hamilton County tap water: hardness, PFAS and lead
Hamilton County, Ohio has about 837,359 residents (Census 2024 estimate) and 12 community water systems in EPA records. The largest local system is Cincinnati Public Water System, serving about 800,000 people from surface water.
✓ 0 of 6 largest systems with health-based violationsPFAS detected at 3 of 6 sampled systemsHardness 126–140 mg/L, varies by area
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
How hard is Hamilton County water?
Cincinnati Public Water SystemMeasured (utility report, 2025) · High confidence
126–140 mg/L(varies by area; no single average published)
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
Softener size at 8.2 gpg
For a 3-person home using 57 gallons per person per day and regenerating weekly, you'd remove about 9,815 grains between regenerations. Suggested size: 24,000 grain. Hardness varies by area here, so this uses the harder plant's figure (8.2 gpg). If your address gets softer water, a smaller unit may do; check your area in the utility report or test your tap.
Estimate only. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
The 6 biggest of 12 community water systems on EPA records for this county. Service areas don't follow county lines; your water bill names your provider.
Cincinnati Public Water System
OH3102612 · serves about 800,000 people · Surface water
✓ No health-based violations✓ Lead below action levelPFAS detected (3 types)
Lead 90th percentile: 2.1 ppb (period starting 2026-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
PFOS: highest sample 6.1 ppt (2 of 6 samples); federal limit 4.0 ppt as a running annual average
PFBA: highest sample 5.2 ppt (2 of 6 samples); no federal limit
PFBS: highest sample 4.1 ppt (2 of 6 samples); no individual limit; counted in EPA's PFAS mixture (hazard index) limit
OH3101112 · serves about 15,000 people · Groundwater
✓ No health-based violations✓ Lead below detectionPFAS detected (5 types)
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2026-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
PFOS: highest sample 12.4 ppt (2 of 2 samples); federal limit 4.0 ppt as a running annual average
PFBA: highest sample 5.7 ppt (1 of 2 samples); no federal limit
PFPeA: highest sample 4.8 ppt (2 of 2 samples); no federal limit
PFBS: highest sample 4 ppt (2 of 2 samples); no individual limit; counted in EPA's PFAS mixture (hazard index) limit
PFHxA: highest sample 3 ppt (1 of 2 samples); no federal limit
OH3100812 · serves about 11,600 people · Groundwater
✓ No health-based violations✓ Lead below detection✓ No PFAS detected
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2026-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
A PFAS detection is not a violation. Federal limits (4 ppt for PFOA and PFOS) apply to running annual averages, with compliance required by 2029. In May 2026 EPA proposed extending the PFOA/PFOS deadline to 2031 and removing other PFAS limits; not final as of 2026-10-21.
Test your own tap
These are public records for whole systems. Your home's pipes, fixtures and any private well can change what you drink. A certified lab test or a hardness test strip gives you your own numbers. Then use our PFAS and lead filter selector to see which certifications to look for.
Common questions about Hamilton County water
Is tap water in Hamilton County safe to drink?
None of the 6 largest systems here have a health-based violation in EPA records since October 2021. Cincinnati Public Water System's most recent lead 90th percentile was 2.1 ppb (2026), below the 15 ppb action level. Public records can't guarantee what comes out of your tap, especially with older plumbing, so a home test is the surest check.
How hard is the water in Hamilton County?
Cincinnati Public Water System reports hardness from 126 to 140 mg/L depending on where you live, with no single system-wide average, so check your area in its report or test your water. For a 3-person home at 8.2 gpg (the harder plant's figure, since your address may get either), our softener calculator suggests a 24,000 grain unit as a starting point.
Is there PFAS in Hamilton County water?
3 of the 6 sampled systems listed here detected at least one PFAS in EPA's UCMR 5 testing, and 2 results were above the level of a federal limit in at least one sample. A detection isn't a violation: federal PFAS limits apply to running annual averages starting in 2029.
Which water system serves my address in Hamilton County?
Most homes are served by Cincinnati Public Water System or one of the other systems listed on this page, but service areas don't follow county lines. Your water bill names your provider, and its annual Consumer Confidence Report has the full test results.
Data as of October 21, 2026. Figures are copied from public records and combined with our own calculations; they can be out of date or wrong. Tapped Out isn't affiliated with any utility or the EPA. Written and reviewed by the Tapped Out team. How we calculate · All sources.