Water system
Hamilton Public Water System
EPA ID OH0904012 · Butler County · 62,447 people served · owned by a local government
Hamilton Public Water System treats its own water from Great Miami Buried Valley Aquifer (wells).
The system's record
- Aquifer
- Great Miami Buried Valley Aquifer
- Active wells
- 21
- Serves
- 62,447 people · Butler County
- EPA ID
- OH0904012
About this area's water
Did you know
- Hamilton's tap water won gold for Best Municipal Water at the 25th anniversary Berkeley Springs International Water Tasting, the competition's silver-jubilee year.
- Unlike most U.S. utilities, Hamilton disinfects with chlorine dioxide instead of chlorine — a choice locals credit for the water's mild flavor.
- The city has run its own waterworks since 1884, pulling from 21 wells in the Great Miami Buried Valley Aquifer through 289 miles of water main to about 25,000 customers.
- Hamilton's wastewater plant returns about 8.5 million gallons a day to the Great Miami River and can swallow up to 48 million gallons on a severe storm day.
History3
- 1884Hamilton has owned and operated its own municipal water utility continuously since 1884, drawing on the Great Miami Buried Valley Aquifer.
- 2015Hamilton's tap water took the gold medal for Best Municipal Water at the 25th anniversary Berkeley Springs International Water Tasting in West Virginia.
- 2020sOhio EPA awarded Hamilton a $500,000 lead service line replacement grant, matched by $500,000 in city funds, targeting about 100 properties in the 45011 and 45015 ZIP codes.
Treatment & pressure
How it is treated
Groundwater from 21 wells in the Great Miami Buried Valley Aquifer feeds two lime-softening plants: the South WTP (40 MGD, 16 production wells in Fairfield) and the North WTP (6 MGD, 5 on-site wells). Water is softened, stabilized, filtered, disinfected with chlorine dioxide rather than chlorine…
Water pressure
not published — the city publishes plant capacities (40 MGD South, 6 MGD North) and 289 miles of water main, but no system-wide average psi figure in materials reviewed.
What it costs
The city's utilities-rates page states rates combine fixed and usage-based charges but publishes no per-ccf or per-1,000-gallon figure; the schedule lives in…
Water quality & impurities
EPA compliance record
Lead at the tap: 90th-percentile result 2 ppb in 2024 (action level 15 ppb).
EPA record: no health-based violations since 2015.
2 violations of any kind logged since 2020: 1 for required testing that was missed or reported late; 1 for a report, record or notice that was missing, late or incomplete (the yearly water quality report, a public notice, lead line records).
Projects & plans3
Recent and current work
- Lead service line replacement program · $1 million · under construction
$500,000 Ohio EPA grant covers the private-side line (curb stop to building); $500,000 city match covers the public right-of-way portion. ~100 properties. - Lead service line replacement during water main renewal · under construction
City replaces known city-owned lead lines whenever it replaces the connecting water main, and supplies filter pitchers to affected customers.
Planned or needed
- Continued lead service line inventory and replacement · planned
City maintains an interactive lead service line map, updated as data improves. Private-side replacement cost remains the owner's responsibility.
Supply stress
Low relative stress: the Great Miami Buried Valley Aquifer is a large, well-recharged groundwater source and the system averages 18.5 MGD against 46 MGD of combined plant capacity. The vulnerability named in city sources is legacy lead service lines in older neighborhoods, not source-water scarcity.
Sewers
Sanitary
Hamilton runs its own Water Reclamation Facility, returning an average of 8.5 million gallons per day of treated water to the Great Miami River and able to accept up to 48 MGD during severe storms, plus about six dry tons of solids daily for reuse. The Water Reclamation Division also operates a satellite wastewater plant and seven…
Storm
The city operates one storm water pump station alongside its wastewater system. We found no dedicated citywide stormwater utility fee.
Sourcesverified
Compiled from the utility's own reports and public records, then independently re-checked against primary sources.
Main supplier in 2 ZIP codes
Serves
Main water supplier in 2 ZIP codes
- 45015 · Hamilton97% of residents
- 45013 · Hamilton59% of residents
Also present in 2 more ZIP codes
- 45011 · Liberty Township and Hamilton30% of residents
- 45014 · Fairfield1% of residents
Population-weighted resident shares; a ZIP code can have more than one system on record. Recomputed from each ZIP's own system list, not from the map's cached footprint.
Buys from · Sells to
Hamilton Public Water System does not buy water from another system on record; it treats its own source water.
1 system on record buys water from Hamilton Public Water System: Butler Co. Water District 2.
What the records show about Hamilton Public Water System
Who runs it
EPA's record describes Hamilton Public Water System as owned by a local government. It has 24,433 service connections and serves 62,447 people.
EPA classes it as a community water system, one that serves the same residents all year.
EPA's record says it has substantially implemented source water protection under Ohio's program, dating the program from 2025.
Source: EPA Safe Drinking Water Information System (SDWIS), water system record.
How the water is treated
EPA's treatment table registers these steps for Hamilton Public Water System: aeration, chlorine dioxide, coagulation and settling, fluoridation, lime softening, and sand or media filtration.
The list is what each system registered with EPA for treatment plants EPA still shows as active, and it can lag a plant upgrade.
Source: EPA Safe Drinking Water Information System (SDWIS) treatment table (EPA Envirofacts, pulled September 2026).
Violations
EPA's record shows no health-based violations for Hamilton Public Water System since 2015.
EPA logs 2 violations of any kind since 2020: 1 for required testing that was missed or reported late; 1 for a report, record or notice that was missing, late or incomplete (the yearly water quality report, a public notice, lead line records).
Source: EPA Safe Drinking Water Information System (SDWIS) violation records: health-based violations with compliance periods beginning in 2015 or later, all violations from 2020 or later (EPA Envirofacts, pulled September 2026).
Lead and copper at the tap
In the sampling period ending December 2024, the 90th-percentile lead result at Hamilton Public Water System was 2 ppb, under both the current 15 ppb action level and the 10 ppb level that applies from 2027.
The highest result on file is 5.3 ppb, in the period ending December 2021.
EPA has 3 sampling periods on file for Hamilton Public Water System since 2016, the first ending in 2018; no period was above 10 ppb.
Every water system has to inventory its service lines, the pipes from the main to each building. In the inventory Hamilton Public Water System sent EPA, 23,072 lines are counted.
| Material | Lines |
|---|---|
| Lead | 4,156 |
| Galvanized, needing replacement | 11 |
| Unknown material | 7,230 |
| Not lead | 11,675 |
| All lines | 23,072 |
Systems sample taps in the homes most likely to have lead pipes or solder. The 90th-percentile result is the level nine in ten of the sampled homes were at or below. Lead comes mostly from service lines and house plumbing, not the source water, so a low result for the system does not clear an old house.
EPA's dashboard status for this inventory: reported all required service line types.
Source: EPA Safe Drinking Water Information System (SDWIS) lead and copper 90th-percentile results (EPA Envirofacts), sampling periods ending 2016 or later; EPA's service line inventory dashboard, Ohio's 2026 Q2 submission.
PFAS
EPA's fifth national round of testing (UCMR 5) took 4 samples of the water entering the pipes of Hamilton Public Water System in 2024 and measured 29 PFAS.
The highest PFOA or PFOS result, 5.3 ng/L, is at or above the federal limit of 4 ng/L that EPA set in 2024. Systems have until 2029 to comply, and in May 2026 EPA proposed letting systems apply for two more years. One sample over the limit is not a violation: compliance is judged on a running annual average.
The highest PFAS results were PFOA 5.3 ng/L, PFHxS 4.1 ng/L, and PFBS 3.6 ng/L.
The highest PFOA or PFOS result was measured at South Plant.
Ohio EPA's own statewide sampling tested 2 plants of Hamilton Public Water System (latest sample July 2020). Not one of the six PFAS tested (PFOA, PFOS, PFHxS, PFNA, GenX and PFBS) was detected.
Ohio EPA's current sampling status map lists 2 plants of Hamilton Public Water System as sampled, most recently February 2026.
| Compound | Highest result | Federal limit |
|---|---|---|
| PFOA | 5.3 ng/L | 4 ng/L |
| PFOS | not detected | 4 ng/L |
PFAS are the 'forever chemicals' from firefighting foam, plating shops and non-stick coatings. Results are for water leaving the plant, not your tap.
Source: EPA UCMR 5 occurrence data (final release, August 2026); Ohio EPA statewide PFAS sampling, 2019 to 2021, and its sampling status map.
Disinfection byproducts
Chlorine that disinfects water also reacts with organic matter to form byproducts. Two groups have federal limits: total trihalomethanes (TTHM, 80 µg/L) and five haloacetic acids (HAA5, 60 µg/L), judged on running yearly averages at each sampling site.
For TTHM, the average of Hamilton Public Water System's samples in 2019, the last year it was sampled, was 0 µg/L. The worst yearly average was 0.4 µg/L and the highest single sample was 2.7 µg/L, from 58 samples taken from 2012 to 2019.
For HAA5, the average in the last year sampled was 0 µg/L. The worst yearly average was 1.1 µg/L and the highest single sample was 3.8 µg/L, from 58 samples.
| Byproduct | Limit | Latest yearly average | Worst yearly average | Highest sample | Samples |
|---|---|---|---|---|---|
| TTHM | 80 µg/L | 0 µg/L (2019) | 0.4 µg/L | 2.7 µg/L | 58 |
| HAA5 | 60 µg/L | 0 µg/L | 1.1 µg/L | 3.8 µg/L | 58 |
A yearly average of 0 means nothing was detected in that year's samples. EPA's file stops at 2019; Ohio EPA's Drinking Water Watch has newer results.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, distribution-system samples (non-detects counted as zero).
Nitrate, arsenic and radioactivity
Nitrate: the highest of 15 samples was 1.5 mg/L (as nitrogen), in 2019, the last year sampled. No sample was over the limit of 10 mg/L. Nitrate above 10 is unsafe for infants.
Arsenic was not detected in 4 samples (limit 10 µg/L).
| Contaminant | Samples | Highest result | Limit | Samples over limit |
|---|---|---|---|---|
| Nitrate (as nitrogen) | 15 | 1.5 mg/L | 10 mg/L | 0 |
| Arsenic | 4 | not detected | 10 µg/L | 0 |
Measured in finished water: at the plant's entry points and in the distribution system; raw well and intake samples are left out. Non-detects count as zero.
EPA's file lumps the entry-point samples of all 2 plants of Hamilton Public Water System together, so a result over a limit may come from a plant that serves a different part of town.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, finished water.
Solvents and fuels
EPA's file holds results for all six solvent and fuel compounds it checked. Benzene, carbon tetrachloride, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, and vinyl chloride were not detected in 4 samples each.
| Compound | Limit | Samples | Detected in | Highest result | Samples over limit |
|---|---|---|---|---|---|
| Benzene | 5 µg/L | 4 | 0 of 4 | not detected | 0 |
| Carbon tetrachloride | 5 µg/L | 4 | 0 of 4 | not detected | 0 |
| 1,2-dichloroethane | 5 µg/L | 4 | 0 of 4 | not detected | 0 |
| Trichloroethylene (TCE) | 5 µg/L | 4 | 0 of 4 | not detected | 0 |
| Tetrachloroethylene (PCE) | 5 µg/L | 4 | 0 of 4 | not detected | 0 |
| Vinyl chloride | 2 µg/L | 4 | 0 of 4 | not detected | 0 |
"Not detected" means the lab's result was below what its method can measure, not that the compound is absent. Non-detects count as zero in the highest-result column.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, finished water.
Farm chemicals and metals
EPA's file holds results for 8 of the nine herbicides and metals it checked. Detected: barium in 2 of 4 samples, highest 57.2 µg/L (limit 2,000). Not detected: atrazine, alachlor, chromium, cadmium, mercury, selenium, and thallium, in 4 samples each.
| Substance | Kind | Limit | Samples | Detected in | Highest result | Samples over limit |
|---|---|---|---|---|---|---|
| Atrazine | Farm chemical | 3 µg/L | 4 | 0 of 4 | not detected | 0 |
| Alachlor | Farm chemical | 2 µg/L | 4 | 0 of 4 | not detected | 0 |
| Chromium | Metal | 100 µg/L | 4 | 0 of 4 | not detected | 0 |
| Cadmium | Metal | 5 µg/L | 4 | 0 of 4 | not detected | 0 |
| Barium | Metal | 2,000 µg/L | 4 | 2 of 4 | 57.2 µg/L | 0 |
| Mercury | Metal | 2 µg/L | 4 | 0 of 4 | not detected | 0 |
| Selenium | Metal | 50 µg/L | 4 | 0 of 4 | not detected | 0 |
| Thallium | Metal | 2 µg/L | 4 | 0 of 4 | not detected | 0 |
Non-detects count as zero in the highest-result column.
EPA's file lumps the entry-point samples of all 2 plants of Hamilton Public Water System together, so a result over a limit may come from a plant that serves a different part of town.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, finished water.
Bacteria in the pipes
From 2012 to 2019, 9 of 6,869 routine total coliform samples taken in the distribution system at Hamilton Public Water System tested positive (0.13%); in 2019, the last year on file, 2 of 853 did. E. coli was never found in the 11 samples tested for it.
A positive coliform test is a warning sign, not a violation by itself. E. coli is a sign that human or animal waste may have reached the water. Coliform counts are routine samples only; E. coli counts include repeat samples.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, distribution-system presence/absence tests for total coliform and E. coli.
Fluoride
The Ohio Department of Health's report to the CDC (My Water's Fluoride) says Hamilton Public Water System adjusts the fluoride level to the recommended level for preventing tooth decay.
EPA's treatment table lists fluoridation among the steps at Hamilton Public Water System.
Measured fluoride: 0.8 mg/L on average at the plant's entry points in 2018 (in the range dentists aim for); samples ran from 0.78 to 1.8 mg/L across 4 samples in 2012 to 2019.
The recommended level for preventing tooth decay is 0.7 mg/L; the federal limit is 4 mg/L. The treatment list is what each system registered with EPA and can lag a plant upgrade.
Source: CDC My Water's Fluoride (fluoridation status as reported by the Ohio Department of Health, fetched September 2026); EPA Safe Drinking Water Information System (SDWIS) treatment table; EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, entry-point fluoride samples.
Lithium
Lithium was not detected in 4 UCMR 5 samples at Hamilton Public Water System, last sampled in 2024 (the method reports from 9 µg/L).
Lithium is not regulated. EPA's draft health reference level is 10 µg/L, and it occurs naturally in deep groundwater, so well systems in the northwest run highest.
Source: EPA UCMR 5 occurrence data (final release, August 2026), samples from 2023 to 2025.
How well the service area is mapped
The service area drawn on the map for Hamilton Public Water System comes from the utility's own map.
Counting the people who live in the ZIP codes it overlaps, this atlas estimates 65,567 residents are inside the boundary, 105% of the 62,447 people Hamilton Public Water System reports serving.
The resident count is an estimate from 2020 Census ZIP-code populations, not a count of customers.
Source: EPA Service Area Boundaries; resident estimate by this atlas from ZIP-code overlap.
On the map
Show this system's territory on the map — 4 ZIP codes in all.
Sources
U.S. EPA SDWIS and Community Water System Service Area Boundaries (v3, 2026), Ohio EPA primacy data, 2020 census blocks: the system serving most residents, traced through purchases to the treating utility; Ohio EPA 2023 Sewer and Water Rate Survey (Ohio State, May 2025) for household bills; Ohio EPA DEFA loan awards since 2016 for the loans paragraph · EPA SDWIS · EPA service area boundaries · Ohio EPA drinking water · Ohio EPA rate survey
EPA's own record for this system: Enforcement and Compliance History report for OH0904012 (EPA ECHO).
Hamilton Public Water System's own pages: hamilton-oh.gov, data.epa.gov
