Warren County Water System water quality
Mason, OH · serves 99,000 people (35,458 connections) · Groundwater · Local government · EPA ID OH8301512
Data: U.S. EPA · How we read the data · How we check it
Summary
No federal limits exceeded in EPA data.
- PFAS
- Not detectedNone of 29 PFAS found above EPA's reporting limits in 2 samples (2023–2025).
- Lead
- Below action level1.4 ppb (parts per billion) at the 90th percentile: 9 in 10 homes sampled were at or below it. Action level 15 ppb, falling to 10 ppb in Nov 2027. Monitoring period ending Jun 2026. Your home's pipes can make yours higher.
- Violations
- None health-basedNo health-based violations since 2016.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read Warren County Water System's annual water quality report (Consumer Confidence Report). It lists every regulated contaminant tested and is usually on the utility's website or mailed with your bill, and you can also request it at (513) 695-1377. EPA: how to find it.
PFAS (“forever chemicals”)
EPA UCMR 5: 1 entry point tested May 2023 to Nov 2023. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA Not detected Limit 4 ppt | – |
| PFOS Not detected Limit 4 ppt | – |
| PFHxS Not detected Limit 10 ppt | – |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Not detected Limit 1 | – |
| PFBS Not detected Guideline 2,000 ppt | – |
| PFBA Not detected Guideline 6,000 ppt | – |
| PFHxA Not detected Guideline 3,000 ppt | – |
29 PFAS tested, 0 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Not detected in 2 samples (reporting limit 9 ppb). About lithium.
Lead and copper
Latest 90th percentile: 1.4 ppb lead (Jan 2026 – Jun 2026). Below action level
1 reported result in EPA's records is far above anything physically plausible (likely a unit or data-entry error) and is not used in the summary.
Highest since 2016: 7 ppb (Dec 2021).
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2026 – Jun 2026 | 1.4 ppb |
| Jul 2025 – Dec 2025 | 1.4 ppb |
| Jan 2025 – Jun 2025 | 2 ppb |
Earlier results (9)
| Jul 2024 – Dec 2024 | 1.5 ppb |
| Jan 2024 – Jun 2024 | 1.5 ppb |
| Jul 2023 – Dec 2023 | 1.4 ppb |
| Jan 2023 – Jun 2023 | 2.8 ppb |
| Jan 2022 – Dec 2022 | 6.2 ppb |
| Jan 2021 – Dec 2021 | 7 ppb |
| Jan 2020 – Dec 2020 | 3.7 ppb |
| Jan 2019 – Dec 2019 | 7 ppb |
| Jan 2018 – Dec 2018 | 6.03 ppb |
Copper 90th percentile: 1.46 ppm (Dec 1996), action level 1,300 ppb.
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
1 unresolved monitoring or reporting violation: Consumer Confidence Rule.
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Earlier EPA testing (2013–2020)
| Contaminant | Highest | Guideline |
|---|---|---|
| Manganese | 2.8 ppb | 300 ppb |
| Strontium | 0.36 ppm | 1.5 ppm |
| Chlorate | 52.2 ppb | 210 ppb |
| Molybdenum | 1.61 ppb | 40 ppb |
Where it serves
Mason, South Lebanon, Kings Mills
ZIP codes the system reported serving: 45034, 45036, 45039, 45040, 45065, 45140, 45152
Nearby utilities
- Western Water Company South Lebanon · 4 mi · PFAS above limit
- Loveland City Public Water System Loveland · 6 mi · PFAS above limit
- Indian Hill City Public Water System The Village of Indian Hill · 11 mi · PFAS above limit
- Middletown City Public Water System Trenton · 12 mi
- Milford City Public Water System Milford · 13 mi · PFAS above limit
- Butler County Water District 2 Public Water System Hamilton · 14 mi
Questions
Is Warren County Water System water safe to drink?
Warren County Water System has no health-based violations since 2016. EPA testing found no PFAS above the federal limits. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does Warren County Water System water have PFAS?
EPA tested Warren County Water System for 29 PFAS between May 2023 and Nov 2023 and none were detected above the reporting limits (about 2 to 20 ppt depending on the chemical).
What is the lead level in Warren County Water System water?
The most recent 90th-percentile lead result for Warren County Water System is 1.4 ppb, for the period ending Jun 2026. The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for OH8301512: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID OH8301512).
- EPA SDWIS download: the lead results, population and violation records we use.
- The utility's annual water quality report (Consumer Confidence Report): ask Warren County Water System at (513) 695-1377, or see EPA's guide to finding it.
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.