Delaware Water Quality Rankings 2026: Best & Worst Cities

This page ranks the 9 Delaware cities whose water systems we have matched to EPA records. Every city starts at 100 points and loses points for health-based EPA violations in the last five years (SDWIS 2026Q2), its most recent Lead and Copper Rule 90th-percentile result, PFAS detected in EPA's 2023–2026 UCMR5 monitoring, and 2012–2019 compliance samples that averaged near or above a limit. Letters follow fixed bands (A ≥90, B ≥80, C ≥70, D ≥60, F below 60). Cities run from the highest score (Dover) down to the lowest (Georgetown); ties are ordered by population served. See the full scoring methodology for every deduction and the data vintages. 1 further Delaware city is listed at the bottom without a grade because we have not yet matched it to an EPA water system.

What your city's grade means

An A or B grade points to water that consistently tests within federal safety limits, while a C suggests moderate issues worth watching and a D or F flags contaminants or compliance problems serious enough to act on. These grades describe system-level water leaving the treatment plant — they can't account for your home's own plumbing, so older houses with lead service lines or fixtures can add contaminants after the water arrives. For a contaminant-by-contaminant view, see the Delaware contaminant breakdown or drill into the county-level rankings.

What Delaware residents should do

• Find your city in the ranking below and open its full report for its violation history, lead results and PFAS table.
• See how Delaware compares against the best-rated and worst-rated cities nationwide.
• Test your home's water if you have concerns — the most common issues involve lead, PFAS, and arsenic.
• Check whether your utility still has lead service lines in Delaware — EPA's inventory counts lead pipes by water system, a risk that plant-level grades cannot capture. Read the lead guide for testing and filter options.
• If treatment makes sense for your situation, compare certified water filters matched to the contaminants found in your area.

We track 10 cities in Delaware. 9 of them are matched to an active EPA-registered community water system (PWSID). Those 9 systems report serving 246,287 people in EPA's Safe Drinking Water Information System (SDWIS).

Of 9 cities of the 10 Delaware cities we can grade from EPA records, 6 cities (67%) grade B or better, 3 sit in the C range and 0 grade D or F. The average score is 87/100. 1 city is not graded because it has not been matched to an EPA system yet.

None of the 9 graded systems has a health-based EPA violation in the last five years; the 1 violation on file in that window is monitoring or reporting lapses.

9 cities have a Lead and Copper Rule 90th-percentile result from 2020 or later: none at 5 ppb or more — every reported result is well below the action level.

EPA's UCMR5 PFAS monitoring (2023–2026) covers 9 cities: PFAS were detected in 6 cities, and PFOA or PFOS reached EPA's 4 ppt limit in 4 cities.

Dover scores highest (100) and Smyrna lowest (74), a 26-point spread.

Lead pipes are the part of tap-water risk a treatment-plant grade cannot see, so start with EPA's service line inventory (Q2 2026 snapshot). 285 Delaware systems inventoried 338,534 service lines: 2,691 confirmed lead plus 3,605 galvanized lines requiring replacement, spread across 12 systems. The bigger number is 113,365 lines (34%) whose material is still unknown — more than one line in four — and EPA treats unknown lines as possible lead until a utility verifies them.

Of the 9 city-linked Delaware utilities with an inventory on file, 9 report at least one lead or galvanized-requiring-replacement line. The largest, WILMINGTON WATER DEPARTMENT (Wilmington, 107,976 served), reports 1,708 lead lines and 669 galvanized requiring replacement.

The best water quality in Delaware is found in Dover with a score of 100/100 and a grade of A. This puts Dover among the top-performing cities in the country for drinking water safety.

The most concerning water quality is in Georgetown scoring 74/100 with a grade of C. Residents may want to consider home water testing and filtration options.

The statewide average score is 87/100, which is 1 points below the national average of 88/100. Only 44% of Delaware cities score above the national average, suggesting statewide water quality improvement is needed.