Water system
Delaware City
EPA ID OH2100311 · Delaware County · 43,895 people served · owned by a local government
Delaware City treats its own water from Olentangy River (blended with deep wells).
The system's record
- Aquifer
- local deep wells (>200 ft) blended with river water
- Water bodies
- Olentangy River
- Raw intakes
- Olentangy
- Active wells
- 5
- Serves
- 43,895 people · Delaware County
- EPA ID
- OH2100311
About this area's water
Did you know
- Delaware pushes its river water through two membrane stages, ultrafiltration then nanofiltration, a far more aggressive filtration train than most Ohio river systems run.
- Well water is treated on a completely separate line - iron and manganese pressure filters, then its own nanofiltration - before the two finished streams meet in one clearwell.
- Backup wells sit both under the plant and in a wellfield on Penry Road two miles north, so a bad day on the Olentangy need not be a bad day at the tap.
- Del-Co Water Company, the big regional nonprofit serving the countryside around Delaware, is a separate utility on entirely different sources - easy to confuse with the city plant.
History4
- 1808Town of Delaware platted; the modern water system comes well over a century later.
- 2024City completes its federally required lead service line inventory in November and begins notifying affected customers.
- 2025Ohio EPA records a Tier 3 monitoring-and-reporting violation for the January 2025 lead service line notification period.
- 2026That violation is resolved in January; the city states it was a notification requirement, not a drinking water quality problem.
Treatment & pressure
How it is treated
River water gets aluminum chlorohydrate coagulation, settling, then ultra- and nanofiltration membranes; well water gets iron/manganese pressure filters plus its own NF membranes. The two streams merge, then chlorine, fluoride and a corrosion inhibitor.
Water pressure
Not published; no psi figure or pressure-zone map found. The city cites 190 miles of water line and 2,000 fire hydrants in its distribution system.
What it costs
No per-1,000-gallon schedule is published online. Bills combine water, wastewater, stormwater and curbside refuse; delinquent bills draw a 5% penalty.
Water quality & impurities8
| Contaminant | Level | Limit | Year |
|---|---|---|---|
| TTHM (total trihalomethanes) Range 7-30.4 ppb; comfortably under the limit for a surface-water source. | 19.4 ppb | 80 | 2025 |
| HAA5 (haloacetic acids) Range ND-12.1 ppb. | 9.33 ppb | 60 | 2025 |
| Lead (90th percentile) Range ND-3.1 ppb; 0 of 32 sites above the action level. | ND ppb | 15 (action… | 2024 |
| Copper (90th percentile) Range 0.011-0.110 ppm; 0 of 32 sites above the action level. | 0.099 ppm | 1.3 (action… | 2024 |
| Nitrate Range ND-1.26 ppm; low for a farmed watershed. | 0.41 ppm | 10 | 2025 |
| Atrazine Herbicide runoff from row crops; range ND-0.7 ppb, detected every year. | 0.2 ppb | 3 | 2025 |
| Fluoride Range 0.84-1.23 ppm; added to prevent tooth decay. | 0.98 ppm | 2.0 (secondary… | 2025 |
| Hardness (as CaCO3) Range 77-162 ppm - hard water, as the limestone bedrock would suggest. | 118 ppm | no standard | 2024 |
EPA compliance record
Lead at the tap: 90th-percentile result 0 ppb in 2024 (action level 15 ppb).
EPA record: no health-based violations since 2015.
1 violation of any kind logged since 2020: 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 & plans1
Recent and current work
- Lead service line inventory and customer notification · 2024-2026 · completed
Nov 2024 inventory and required notices; a Tier 3 monitoring/reporting violation for Jan 2025 was resolved in Jan 2026.
Supply stress
The Olentangy is a developed farm-and-suburb watershed and Ohio EPA rates the city's supply as highly susceptible to contamination; atrazine turns up every year. Deep wells under the plant and a Penry Road wellfield give a groundwater fallback most river-fed Ohio systems lack.
Sewers
Sanitary
The city's own sewer division collects and treats wastewater and returns it to the Olentangy River, over 175 miles of sewer line, 3,250 manholes and 12 pump stations.
Storm
Separate storm sewers, billed as a stormwater charge on the utility bill. The city maintains a stormwater management plan and an illicit discharge detection and elimination plan under federal MS4 rules.
Sourcesverified
Compiled from the utility's own reports and public records, then independently re-checked against primary sources.
Main supplier in 1 ZIP code
Serves
Main water supplier in 1 ZIP code
- 43015 · Delaware55% 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
Delaware City does not buy water from another system on record; it treats its own source water.
No other system is on record buying water from Delaware City.
What the records show about Delaware City
Who runs it
EPA's record describes Delaware City as owned by a local government. It has 16,216 service connections and serves 43,895 people.
EPA classes it as a community water system, one that serves the same residents all year.
Its office telephone on EPA's record is 740-203-1926.
Source: EPA Safe Drinking Water Information System (SDWIS), water system record.
How the water is treated
EPA's treatment table registers these steps for Delaware City: aeration, corrosion control, cartridge filtration, coagulation and settling, chlorine disinfection, dechlorination, iron and manganese removal, fluoridation, membrane filtration, reverse osmosis, 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 Delaware City since 2015.
EPA logs 1 violation of any kind since 2020: 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 Delaware City was 0 ppb, under both the current 15 ppb action level and the 10 ppb level that applies from 2027. A result of 0 means at least nine in ten of the homes sampled had no lead detected.
EPA has 5 sampling periods on file for Delaware City since 2016, the first ending in 2016; 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 Delaware City sent EPA, 15,297 lines are counted.
| Material | Lines |
|---|---|
| Lead | 43 |
| Galvanized, needing replacement | 169 |
| Unknown material | 12,049 |
| Not lead | 3,036 |
| All lines | 15,297 |
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 Delaware City in 2023 to 2024 and measured 29 PFAS. No PFAS was detected, PFOA and PFOS (federal limit 4 ng/L each) among them.
Ohio EPA's own statewide sampling tested 1 plant of Delaware City (latest sample October 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 1 plant of Delaware City as sampled, most recently February 2024.
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 Delaware City's samples in 2019, the last year it was sampled, was 15.2 µg/L. The worst yearly average was 80.3 µg/L and the highest single sample was 127.6 µg/L, from 152 samples taken from 2012 to 2019. A yearly average over 80 is not itself a violation, because compliance is judged site by site.
For HAA5, the average in the last year sampled was 5.2 µg/L. The worst yearly average was 34 µg/L and the highest single sample was 47.8 µg/L, from 152 samples.
| Byproduct | Limit | Latest yearly average | Worst yearly average | Highest sample | Samples |
|---|---|---|---|---|---|
| TTHM | 80 µg/L | 15.2 µg/L (2019) | 80.3 µg/L | 127.6 µg/L | 152 |
| HAA5 | 60 µg/L | 5.2 µg/L | 34 µg/L | 47.8 µg/L | 152 |
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 97 samples was 5.2 mg/L (as nitrogen) in 2013; in 2019, the last year sampled, the highest was 0.7 mg/L. No sample was over the limit of 10 mg/L. Nitrate above 10 is unsafe for infants.
Arsenic was not detected in 8 samples (limit 10 µg/L).
| Contaminant | Samples | Highest result | Limit | Samples over limit |
|---|---|---|---|---|
| Nitrate (as nitrogen) | 97 | 5.2 mg/L | 10 mg/L | 0 |
| Arsenic | 8 | 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.
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 8 samples each.
| Compound | Limit | Samples | Detected in | Highest result | Samples over limit |
|---|---|---|---|---|---|
| Benzene | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Carbon tetrachloride | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| 1,2-dichloroethane | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Trichloroethylene (TCE) | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Tetrachloroethylene (PCE) | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Vinyl chloride | 2 µg/L | 8 | 0 of 8 | 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: atrazine in 14 of 25 samples, highest 6.7 µg/L (limit 3, 1 over); barium in 5 of 8 samples, highest 15 µg/L (limit 2,000). Not detected: alachlor in 25 samples, chromium in 8 samples, cadmium in 8 samples, mercury in 8 samples, selenium in 8 samples, thallium in 8 samples.
| Substance | Kind | Limit | Samples | Detected in | Highest result | Samples over limit |
|---|---|---|---|---|---|---|
| Atrazine | Farm chemical | 3 µg/L | 25 | 14 of 25 | 6.7 µg/L | 1 |
| Alachlor | Farm chemical | 2 µg/L | 25 | 0 of 25 | not detected | 0 |
| Chromium | Metal | 100 µg/L | 8 | 0 of 8 | not detected | 0 |
| Cadmium | Metal | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Barium | Metal | 2,000 µg/L | 8 | 5 of 8 | 15 µg/L | 0 |
| Mercury | Metal | 2 µg/L | 8 | 0 of 8 | not detected | 0 |
| Selenium | Metal | 50 µg/L | 8 | 0 of 8 | not detected | 0 |
| Thallium | Metal | 2 µg/L | 8 | 0 of 8 | not detected | 0 |
Non-detects count as zero in the highest-result column.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, finished water.
Bacteria in the pipes
From 2012 to 2019, 3 of 3,855 routine total coliform samples taken in the distribution system at Delaware City tested positive (0.08%); in 2019, the last year on file, 0 of 487 did. E. coli was never found in the 3 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 Delaware City adjusts the fluoride level to the recommended level for preventing tooth decay.
EPA's treatment table lists fluoridation among the steps at Delaware City.
Measured fluoride: 1.1 mg/L on average at the plant's entry points in 2019 (in the range dentists aim for); samples ran from 0.79 to 1.1 mg/L across 8 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 found in 1 of 4 UCMR 5 samples at Delaware City, highest 15.4 µg/L, last sampled in 2024.
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.
Algal toxins
Ohio EPA tests for microcystin, a toxin that harmful algal blooms can release, in raw water at the intake and in treated water.
At the intake, microcystin was detected 2 times in 282 raw-water samples, across 2 bloom seasons (2018 to 2025); the highest raw-water result was 0.56 µg/L on January 29, 2018. The highest raw-water result since 2024 was 0.267 µg/L.
Microcystin was never detected in treated water (280 samples).
In all, 562 samples from 2016 to 2026, the latest on August 24, 2026.
| Water | Samples | Detections | Highest result |
|---|---|---|---|
| Raw water, at the intake | 282 | 2 | 0.56 µg/L |
| Treated water | 280 | 0 | not detected |
The ten-day advisory levels for treated water are 0.3 µg/L for children under six and 1.6 µg/L for everyone else. Any detection at the intake triggers more frequent testing until two clean weeks.
Source: Ohio EPA public water system harmful algal bloom monitoring, 2016 to present (HAB data, fetched September 2026).
How well the service area is mapped
The service area drawn on the map for Delaware City comes from the utility's own map.
Counting the people who live in the ZIP codes it overlaps, this atlas estimates 31,607 residents are inside the boundary, 72% of the 43,895 people Delaware City 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.
Photograph
On the map
Show this system's territory on the map — 1 ZIP code 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 OH2100311 (EPA ECHO).
Delaware City's own pages: delawareohio.net, 1808delaware.com, delcowater.org
