01The verdict: is Winterthur water safe?
Winterthur's tap water meets most EPA standards but has areas that warrant attention. With a grade of B+ (82.5/100), some contaminant levels or compliance issues suggest that residents may benefit from additional filtration. The city's 1 water system serves approximately 687 residents using groundwater (wells).
2 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 ↓Top half in Delaware
Winterthur ranks #13 of 40 graded Delaware cities.
See the comparison ↓Lead is approaching its limit
Measured at 12.0 ppb — 80% of the 15 ppb limit. Within the rules, but with less headroom than you'd want.
See the ledger ↓Winterthur's drinking water received a grade of B+ (82.5 out of 100), indicating good water quality. The city's 1 water system serves approximately 687 residents using groundwater.
Lead levels were measured at 12.0 ppb (90th percentile), which is within EPA limits but above recommended levels. This system has not yet been tested for PFAS under the EPA UCMR 5 program. The system has 4 violations on record, including 0 health-based violations. 2 remain unresolved.
Winterthur ranks #13 out of 40 cities in Delaware for water quality, placing it mid-range in the state. Winterthur 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. While lead levels are within EPA limits, they are above the recommended 5 ppb threshold that health organizations consider ideal. A point-of-use filter adds an extra layer of protection. As a small community water system, Winterthur may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
02What's in Winterthur's water
Every contaminant flagged in Winterthur, 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.
Near Limit — EPA Action Level: 15 ppb
Within EPA limits but above the American Academy of Pediatrics recommended level of 1 ppb — no lead level is considered safe for children. An NSF 53-certified filter provides additional protection, and running the cold tap 30 seconds after stagnation reduces exposure.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. | 12.0 | 15 | ppb | Inorganic | Near Limit |
Cities ranked by 90th-percentile lead PF PFAS in Delaware
Cities ranked by compounds detected Cu Copper in Delaware
Cities ranked by 90th-percentile copper
03Winterthur'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 4 violations on record, including 0 health-based violations. 2 remain unresolved.
All ten of the last ten years were clean — no EPA violations recorded for Winterthur.
▼ Down 25 ppb since 1993. Latest reading: 12 ppb (2024) — 80% of the action level. Sampled at higher-risk homes (90th percentile).
04Where Winterthur's water comes from
Winterthur'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.
1 system
1 water system, operated under private ownership.
687 people
Residents served across Winterthur'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 687 people through 1 water system.
| System name | PWSID | Population | Source |
|---|---|---|---|
| WINTERTHUR | DE0000503 | 687 | Groundwater |
Water bodies near Winterthur
These water bodies shape the regional watershed and can indirectly affect groundwater quality.
05Pressure on Winterthur'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.
Flood & storm history
9 federal disaster declarations on record for New Castle County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
Drought
New Castle County is in D2 (severe drought) per the U.S. Drought Monitor (week of Jul 2026). Drought can raise disinfection-byproduct levels and taste/odor issues as utilities draw from lower reservoirs.
06How Winterthur compares
Scores for nearby Delaware cities on one line, with the average marked.
dashed line = Delaware average (75/100)
Winterthur scores 82.5/100 — above the Delaware average of 75/100. It outscores 10 of 10 nearby cities. Full Delaware rankings →
80.5 / 100BWilmington, DE
79.5 / 100BMillville, DE
76.4 / 100CNewark, DE
56.5 / 100BDover, DE
75.3 / 100CDewey Beach, DE
66.8 / 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 Winterthur's water — not generic advice.
Filter drinking & cooking water
Basic carbon filter for extra protection. Lead detected at 12.0 ppb
Compare tested filters →Flush taps & check your service line
Lead leaches from pipes as water sits. Run cold water 30 seconds before drinking (especially mornings), and ask the utility whether your address still has a lead service line.
Lead risks explained →Watch for Winterthur 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 Winterthur, DE tap water safe to drink?
Winterthur's water quality earned a grade of B+ (82.5/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #13 out of 40 cities tested in Delaware.
What contaminants are in Winterthur's water?
Lead was measured at 12.0 ppb (90th percentile). 4 violations are on record.
How is Winterthur'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 Winterthur?
While lead levels are within EPA limits, a filter adds extra protection. Based on current data, basic filtration should suffice for additional peace of mind.
Where does Winterthur's water come from?
Winterthur's water is sourced from Groundwater. The city has 1 water system serving approximately 687 residents.
Is Winterthur's groundwater at risk of contamination?
Winterthur 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 4 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 Winterthur's water compare to other cities?
Winterthur ranks #13 out of 40 cities in Delaware (better than 68% of state cities) and #6879 out of 15382 cities nationally (55th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Winterthur's small water system affect quality?
Winterthur's system serves approximately 687 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 4 violations on record.