Copper in Delaware Drinking Water
Ranked by 90th percentile copper level (mg/L) · Data from EPA SDWIS & UCMR
Copper in Delaware: what the data shows
Delaware has 21 cities with copper monitoring data. The state average 90th percentile copper level is 3.288 mg/L, compared to 28.808 mg/L nationally — better than the national average. 21 cities exceed the EPA action level of 1.3 mg/L. Copper in drinking water typically comes from corrosion of copper pipes and plumbing fixtures, particularly in older homes. The EPA action level of 1.3 mg/L is the 90th percentile threshold — if more than 10% of tap samples exceed it, utilities must take corrective action including adjusting water chemistry to reduce corrosivity. Short-term copper exposure above the action level can cause gastrointestinal distress. Long-term exposure at elevated levels is associated with liver and kidney damage. Flushing your tap for 30 seconds before use and using an NSF 53-certified filter can reduce copper exposure.
Cities exceeding 1.3 mg/L EPA Action Level
Copper data across Delaware
Each dot is a city, colored by overall water quality grade. Cities with copper levels above the 1.3 mg/L EPA action level are highlighted. Size reflects population served.
Top 10 cities by copper level in Delaware
Highest Copper levels (mg/L)
All Delaware cities ranked by copper level
| # | City | Level | Level | Exceeds? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Frankford | 11.650 mg/L | Yes | 20 | B | |
| 2 | Milford | 7.700 mg/L | Yes | 12 | A- | |
| 3 | Rehoboth Beach | 5.320 mg/L | Yes | 8 | B | |
| 4 | Camden-Wyoming | 4.950 mg/L | Yes | 35 | B | |
| 5 | Bridgeville | 4.310 mg/L | Yes | 6 | B+ | |
| 6 | Delmar | 3.537 mg/L | Yes | 7 | B | |
| 7 | Dagsboro | 3.265 mg/L | Yes | 52 | B | |
| 8 | Dover | 3.210 mg/L | Yes | 35 | B | |
| 9 | Greenwood | 3.147 mg/L | Yes | 20 | B+ | |
| 10 | Middletown | 2.850 mg/L | Yes | 17 | B+ | |
| 11 | Georgetown | 2.648 mg/L | Yes | 56 | F | |
| 12 | Lewes | 2.120 mg/L | Yes | 20 | D+ | |
| 13 | Smyrna | 2.078 mg/L | Yes | 14 | C | |
| 14 | Ellendale | 1.754 mg/L | Yes | 19 | A- | |
| 15 | Dewey Beach | 1.590 mg/L | Yes | 12 | C+ | |
| 16 | New Castle | 1.580 mg/L | Yes | 9 | B- | |
| 17 | Bethany Beach | 1.570 mg/L | Yes | 5 | B+ | |
| 18 | Milton | 1.508 mg/L | Yes | 10 | B | |
| 19 | Millsboro | 1.500 mg/L | Yes | 77 | D | |
| 20 | Seaford | 1.390 mg/L | Yes | 38 | F | |
| 21 | Newark | 1.380 mg/L | Yes | 5 | C- |
Frequently asked questions about copper in Delaware
Is copper in Delaware drinking water safe?
21 cities in Delaware exceed the EPA action level of 1.3 mg/L for copper. The state average is 3.288 mg/L. Copper levels are highest in homes with copper plumbing, particularly when water sits in pipes overnight. Flushing the tap before use significantly reduces copper in drinking water.
What causes high copper levels in Delaware tap water?
Copper typically leaches from copper pipes and brass fittings within homes, not from the water source itself. Corrosive (low pH or soft) water accelerates this leaching. Water utilities with high copper readings are required to adjust water chemistry to reduce corrosivity. You can reduce exposure by flushing your tap for 30 seconds before use.