Cleanest Big-City Tap Water in 2026: The Top-Graded Large US Water Systems

Seven large US water systems earn an A grade from TapWaterSafety in 2026: Glen Burnie-Broadneck (Maryland), Helix Water District (California), Baton Rouge Water Company (Louisiana), Northern Kentucky Water District, Memphis Light, Gas & Water (Tennessee), Howard County D.P.W. (Maryland), and Honolulu’s Windward-Pearl Harbor system (Hawaii). Each serves at least 250,000 people, and none had a single quarter with an EPA violation in the last three years.

That is 7 out of 153 large systems in our data. An A is a strong result, but it is not a promise that the water is free of every contaminant. Below are the systems, their records, and what the grade really tells you.

How we built this list

TapWaterSafety grades 1,000 US utilities, each serving roughly 50,000 people or more.

We set the cutoff at 250,000 people served. That captures the systems behind most large cities and big suburban counties, and it gives a group of 153 systems, large enough to compare fairly. Here is how those 153 systems grade:

Grade	Large systems (250,000+ served)
A	7
B	31
C	54
D	37
F	24

EPA compliance data comes from EPA ECHO compliance records, checked October 7, 2026, covering the last 12 quarters (three years). Population figures are those reported for each system, so they can differ from a city’s census population.

The seven A-grade large systems

1. Glen Burnie-Broadneck, Maryland: A (94)

Serves: 290,606 people (Anne Arundel County area; listed under Millersville)
Source: Groundwater
EPA record: 0 of 12 quarters with a violation. No open violations, not listed as a serious violator, not over the lead action level.
Top concerns: combined radium (-226 and -228) and haloacetic acids (HAA9) above health guidelines.

The highest score among large systems. See the full Glen Burnie-Broadneck report.

2. Helix Water District, California: A (89)

Serves: 277,668 people (La Mesa and nearby San Diego County communities)
Source: Surface water
EPA record: 0 of 12 quarters with a violation. Not a serious violator, not over the lead action level.
Top concerns: haloacetic acids (HAA9 and HAA5) and total trihalomethanes (TTHMs) above health guidelines.

See the Helix Water District report.

3. Baton Rouge Water Company, Louisiana: A (88)

Serves: 596,844 people
Source: Groundwater
EPA record: 0 of 12 quarters with a violation. Not a serious violator, not over the lead action level.
Top concerns: HAA9, HAA5 and TTHMs above health guidelines.

See the Baton Rouge Water Company report.

4. Northern Kentucky Water District: A (87)

Serves: 259,949 people (listed under Fort Thomas)
Source: Surface water
EPA record: 0 of 12 quarters with a violation. Not a serious violator, not over the lead action level.
Top concerns: TTHMs, HAA9 and HAA5 above health guidelines.

See the Northern Kentucky Water District report.

5. Memphis Light, Gas & Water, Tennessee: A (87)

Serves: 659,500 people
Source: Groundwater
EPA record: 0 of 12 quarters with a violation. Not a serious violator, not over the lead action level.
Top concerns: TTHMs, bromodichloromethane and HAA9 above health guidelines.

Memphis is the largest A-grade system on this list. See the Memphis Light, Gas & Water report.

6. Howard County D.P.W. Distribution, Maryland: A (86)

Serves: 286,158 people (listed under Columbia)
Source: Purchased surface water (bought from another utility)
EPA record: 0 of 12 quarters with a violation. Not a serious violator, not over the lead action level.
Top concerns: HAA9, TTHMs and HAA5 above health guidelines.

See the Howard County D.P.W. report.

7. HNL-Windward-Pearl Harbor, Hawaii: A (85)

Serves: 631,389 people (Honolulu)
Source: Groundwater
EPA record: 0 of 12 quarters with a violation. Not a serious violator, not over the lead action level.
Top concerns: hexavalent chromium (chromium-6), PFHxS (a PFAS chemical) and TTHMs above health guidelines.

This system sits right at the A cutoff of 85. See the HNL-Windward-Pearl Harbor report.

Together, these seven systems serve about 3 million people.

The next tier: large systems scoring 80 to 83 (B)

These systems fell just short of an A. Most have clean or nearly clean EPA records. Where a violation is listed, it is a testing, monitoring or reporting violation, not a finding that water exceeded a legal limit.

System	State	Served	Score	Quarters with a violation (of 12)	EPA violations listed
OCUD/Eastern Water System	FL	293,374	83	1	Monitoring/reporting, DBP rule (open since 01/2025)
Metro Water Services (Nashville)	TN	778,153	83	1	Monitoring, DBP and coliform rules (both closed)
JEA Major Grid (Jacksonville)	FL	826,664	82	1	Monitoring/reporting, Ground Water Rule (open since 11/2024)
Orlando Utilities Commission	FL	536,466	82	1	Monitoring, coliform rule (open since 04/2025)
Manatee County Utilities	FL	347,800	82	1	Monitoring, coliform rule (open since 06/2025)
Detroit, City of	MI	633,218	82	0	None
East Bay MUD (Oakland)	CA	1,442,800	81	0	None
DeKalb County	GA	743,000	81	0	None
Water District 1 of Johnson County	KS	490,000	81	0	None
Minneapolis	MN	425,300	80	0	None
Greenville Water	SC	396,265	80	2	Consumer Confidence Report rule (open since 10/2025)
Clarksville Water Department	TN	251,864	80	0	None
Knoxville Utilities Board	TN	254,671	80	0	None

East Bay MUD is the largest system in this group, serving more than 1.4 million people with no EPA violation quarters in three years.

What an A grade means

TapWaterSafety scores each system from 0 to 100 using five weighted parts, described in full on our methodology page:

Health guideline performance (40%): detected contaminants compared with EWG health guidelines, which are usually stricter than legal limits.
Legal compliance (20%): health-based Safe Drinking Water Act violations over the past three years.
High-risk contaminant presence (20%): whether contaminants such as PFAS, lead, arsenic, chromium-6, radium, nitrate above a caution level, or disinfection byproducts above 40 ppb are detected.
Compliance and reporting history (10%): monitoring, reporting and public notice failures over 36 months.
Source water vulnerability (10%): source type and state source-water assessments.

A score of 85 or higher earns an A, which the methodology describes as minimal contamination, full compliance and a low-risk source. In practice, the seven A systems above share two things: a spotless three-year EPA record and relatively few, smaller exceedances of health guidelines.

What an A grade does not mean

It does not mean “nothing detected.” Every A-grade system above still lists contaminants “significantly above health guideline.” These are comparisons to EWG’s health guidelines, which are much stricter than EPA’s legal limits. A system can be fully legal and still show up here. For context on that gap, see EWG vs. EPA: the gap.

Disinfection byproducts are nearly universal. All seven A systems list trihalomethanes or haloacetic acids among their top concerns. These form when chlorine or other disinfectants react with natural material in water. EPA’s legal limits are 80 ppb for TTHMs and 60 ppb for HAA5. HAA9 is a broader group of nine haloacetic acids that has no federal limit; EPA regulates the five in HAA5. Read more in our guide to TTHMs and HAA5.

It does not cover your home’s pipes. Grades describe the water a utility delivers. They do not measure lead at your tap, which usually comes from service lines, solder or fixtures. A home in an A-grade city can still have a lead problem. See how to test for lead.

It reflects the recent past. Grades summarize documented data. They are not a guarantee of current or future water quality, and they will not reflect a treatment change until it shows up in monitoring data.

PFAS rules are still shifting. EPA’s April 2024 PFAS rule set limits of 4 parts per trillion for PFOA and PFOS, plus limits for PFHxS, PFNA, GenX and a mixture of PFAS. In May 2026, EPA proposed keeping the PFOA and PFOS limits but rescinding the others, including PFHxS, and letting some systems request until 2031 to comply. As of October 2026 those changes were proposals, not final rules. Honolulu’s PFHxS concern is worth watching either way.

Records can change

A utility may have resolved an issue since our data was pulled, or new monitoring may show a change. For the latest, check the EPA ECHO report linked on each utility page and the utility’s annual Consumer Confidence Report. Our guide on how to read your water quality report walks through it.

Where does your system rank?

Most Americans get water from a smaller system than the ones on this list. To see your own utility’s grade, score and EPA record, search by ZIP code or city, or browse by state. If your system grades lower, our companion post on the lowest-graded big-city systems covers the most common concerns and which filters match them.