01The verdict: is Delafield water safe?
Delafield's drinking water has significant quality concerns based on EPA testing data. With a grade of D (47/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 17 water systems serve approximately 1,347 residents using groundwater (wells).
85 unresolved violations on record
EPA records show open compliance items for this system. Most are administrative, but unresolved items are worth watching.
See what was cited ↓Lead is well under the limit
90th-percentile lead is 1.2 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓44 violations in the last five years
Recent compliance history is the best predictor of future problems — the year-by-year record is below.
See the record ↓Delafield's drinking water received a grade of D (47 out of 100), indicating poor water quality. The city's 17 water systems serve approximately 1,347 residents using groundwater.
Lead levels were measured at 1.2 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program. The system has 281 violations on record, including 22 health-based violations. 85 remain unresolved.
Delafield ranks #419 out of 441 cities in Wisconsin for water quality, placing it among the lowest-rated in the state. Delafield relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff. As a small community water system, Delafield may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities. The system has seen 44 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
02What's in Delafield's water
Every contaminant flagged in Delafield, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 1.2 | 15 | ppb | Inorganic | Safe |
Cities ranked by 90th-percentile lead PF PFAS in Wisconsin
Cities ranked by compounds detected Cu Copper in Wisconsin
Cities ranked by 90th-percentile copper
03Delafield's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. The system has 281 violations on record, including 22 health-based violations. 85 remain unresolved.
3 of the last ten years were clean. The numbered years had EPA violations — red when any were health-based, amber when they were paperwork or missed-testing issues.
▼ Down 1.8 ppb since 1993. Latest reading: 0.20 ppb (2025) — 1% of the action level. Sampled at higher-risk homes (90th percentile).
04Where Delafield's water comes from
Delafield's drinking water is drawn from underground aquifers through wells.
Groundwater
Underground aquifers reached by wells — naturally filtered, but can carry minerals like arsenic and nitrate.
Local treatment
Groundwater generally needs less treatment — typically disinfection and, where needed, mineral removal.
17 systems
17 water systems (1 wholesaler), operated under private ownership.
1,347 people
Residents served across Delafield's service area.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals. Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds. The system is operated by private ownership and serves approximately 1,347 people through 17 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| DELAFIELD SQUARE | WI2685812 | 587 | Groundwater |
| NASHOTAH HOUSE | WI2682512 | 350 | Groundwater |
| ST JOHNS NORTHWESTERN ACADEMIES | WI2680761 | 340 | Groundwater |
| DELAFIELD WATERWORKS | WI2684642 | 300 | Groundwater |
| ARBORS | WI2682795 | 280 | Groundwater |
| LAKE COUNTRY APARTMENTS | WI2682229 | 84 | Groundwater |
| APARTMENTS OF STONERIDGE | WI2682761 | 75 | Groundwater |
| KNOLLCREST | WI2681104 | 66 | Groundwater |
| DELAFIELD LAKES 402 | WI2686101 | 50 | Groundwater |
| CAMBRIDGE PLACE OF DELAFIELD | WI2686325 | 50 | Groundwater |
| QUAIL HOLLOW CONDOS | WI2686359 | 30 | Groundwater |
| DELAFIELD WOODS 411 | WI2686336 | 28 | Groundwater |
| SANCTUARY OF DELAFIELD | WI2685951 | 27 | Groundwater |
| DELAFIELD WOODS 828 | WI2686337 | 26 | Groundwater |
| DELAFIELD LAKES 404 | WI2686114 | 25 | Groundwater |
| WELLS ST STATION 425 WEST | WI2686466 | 25 | Groundwater |
| WELLS ST STATION 435 EAST | WI2686619 | 25 | Purchased Groundwater |
Water bodies near Delafield
These water bodies shape the regional watershed and can indirectly affect groundwater quality.
05Pressure on Delafield's watershed
Outside forces that shape what reaches the treatment plant. None of these is a verdict on the tap by itself — but each adds pressure worth knowing about.
Industrial discharge
5 facilities within 10 miles reported 89 lb released to surface water in the latest EPA Toxics Release Inventory. Proximity doesn't equal tap contamination — treatment and hydrology decide — but it's pressure on the watershed.
Flood & storm history
7 federal disaster declarations on record for Waukesha County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Delafield compares
Scores for nearby Wisconsin cities on one line, with the average marked.
dashed line = Wisconsin average (65/100)
Delafield scores 47/100 — below the Wisconsin average of 65/100. It outscores 2 of 10 nearby cities. Full Wisconsin rankings →
90.2 / 100FMadison, WI
35.4 / 100DGreen Bay, WI
54 / 100CRacine, WI
69.5 / 100DKenosha, WI
45.8 / 100DWaukesha, WI
47.1 / 100
Compare all cities in the county — grades, violations, and contaminant data side by side.→
07What to do at home
Steps matched to what testing actually found in Delafield's water — not generic advice.
A basic carbon filter still helps
Delafield's water meets federal standards, but a simple carbon filter improves taste and adds a margin of safety against short-term issues.
Compare tested filters →Read your utility's annual report
Every utility must publish a yearly Consumer Confidence Report with its own testing results. It pairs well with the independent data on this page.
How to read a CCR →Watch for Delafield alerts
This area has a history of flood declarations — after severe weather, watch for boil-water advisories from the utility, and check the live alerts on this page.
All water alerts →Frequently asked questions
Is Delafield, WI tap water safe to drink?
Delafield's water quality earned a grade of D (47/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #419 out of 441 cities tested in Wisconsin.
What contaminants are in Delafield's water?
Lead was measured at 1.2 ppb (90th percentile). 281 violations are on record.
How is Delafield's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Delafield?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Delafield's water come from?
Delafield's water is sourced from Groundwater. The city has 17 water systems serving approximately 1,347 residents.
What health violations has Delafield's water system had?
Delafield has 22 health-based violations on record. The most recent violation was recorded in April 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 85 violations remain unresolved.
Is Delafield's groundwater at risk of contamination?
Delafield uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 281 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Delafield's water compare to other cities?
Delafield ranks #419 out of 441 cities in Wisconsin (better than 5% of state cities) and #13502 out of 15382 cities nationally (12th percentile). The grade of D reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.