Least Reliable Water Systems in Maryland — 2026

Out of 615 ZIP codes with data in Maryland, these are the lowest-ranked areas for reliability score. See also: National Least Reliable Water Systems in America | All Maryland Rankings

Statistic	Value
ZIP codes ranked	615
Lowest value	24/100
Median value	75/100
State	Maryland

100 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Reliability Score	Safety Score
1	21917	Colora	MD	24/100	53/100
2	21901	North East	MD	25/100	59/100
3	21903	Perryville	MD	25/100	59/100
4	21639	Greensboro	MD	27/100	89/100
5	21866	Tylerton	MD	36/100	67/100
6	21619	Chester	MD	39/100	80/100
7	20601	Waldorf	MD	40/100	72/100
8	20602	Waldorf	MD	40/100	77/100
9	20603	Waldorf	MD	40/100	72/100
10	20619	California	MD	40/100	53/100
11	21784	Sykesville	MD	40/100	57/100
12	20871	Clarksburg	MD	41/100	64/100
13	21645	Kennedyville	MD	42/100	88/100
14	20639	Huntingtown	MD	44/100	50/100
15	21842	Ocean City	MD	44/100	73/100
16	21913	Cecilton	MD	44/100	56/100
17	20658	Marbury	MD	47/100	71/100
18	20664	Newburg	MD	47/100	72/100
19	20794	Jessup	MD	47/100	59/100
20	21042	Ellicott City	MD	47/100	59/100
21	21043	Ellicott City	MD	47/100	54/100
22	21562	Westernport	MD	49/100	63/100
23	20678	Prince Frederick	MD	50/100	63/100
24	21661	Rock Hall	MD	50/100	78/100
25	21811	Berlin	MD	50/100	78/100
26	21904	Port Deposit	MD	50/100	66/100
27	20650	Leonardtown	MD	51/100	70/100
28	21153	Stevenson	MD	52/100	62/100
29	21157	Westminster	MD	52/100	64/100
30	21158	Westminster	MD	52/100	69/100
31	21911	Rising Sun	MD	52/100	74/100
32	21632	Federalsburg	MD	54/100	88/100
33	21658	Queenstown	MD	55/100	76/100
34	21841	Newark	MD	55/100	90/100
35	21034	Darlington	MD	56/100	62/100
36	20653	Lexington Park	MD	57/100	77/100
37	20657	Lusby	MD	57/100	51/100
38	21078	Havre De Grace	MD	57/100	56/100
39	21629	Denton	MD	57/100	94/100
40	21771	Mount Airy	MD	57/100	69/100
41	21795	Williamsport	MD	57/100	59/100
42	21851	Pocomoke City	MD	58/100	86/100
43	21053	Freeland	MD	59/100	57/100
44	21057	Glen Arm	MD	59/100	68/100
45	21624	Claiborne	MD	59/100	93/100
46	21638	Grasonville	MD	59/100	78/100
47	20670	Patuxent River	MD	60/100	80/100
48	21651	Millington	MD	60/100	88/100
49	21740	Hagerstown	MD	60/100	63/100
50	21742	Hagerstown	MD	60/100	58/100
51	21746	Hagerstown	MD	60/100	64/100
52	21750	Hancock	MD	60/100	63/100
53	21539	Lonaconing	MD	61/100	75/100
54	20622	Charlotte Hall	MD	62/100	82/100
55	20689	Sunderland	MD	62/100	65/100
56	21054	Gambrills	MD	62/100	82/100
57	21090	Linthicum Heights	MD	62/100	77/100
58	21146	Severna Park	MD	62/100	72/100
59	21543	Midlothian	MD	62/100	82/100
60	21557	Rawlings	MD	62/100	82/100
61	21561	Swanton	MD	62/100	82/100
62	21623	Church Hill	MD	62/100	98/100
63	21719	Cascade	MD	62/100	32/100
64	21849	Parsonsburg	MD	62/100	94/100
65	21919	Earleville	MD	62/100	77/100
66	21798	Woodsboro	MD	63/100	64/100
67	21861	Sharptown	MD	64/100	93/100
68	21921	Elkton	MD	64/100	66/100
69	20636	Hollywood	MD	65/100	82/100
70	20711	Lothian	MD	65/100	83/100
71	21154	Street	MD	65/100	70/100
72	21520	Accident	MD	65/100	82/100
73	21540	Luke	MD	65/100	83/100
74	21550	Oakland	MD	65/100	73/100
75	20714	North Beach	MD	67/100	51/100
76	20715	Bowie	MD	67/100	77/100
77	20716	Bowie	MD	67/100	82/100
78	20720	Bowie	MD	67/100	77/100
79	20721	Bowie	MD	67/100	77/100
80	21144	Severn	MD	67/100	77/100
81	21613	Cambridge	MD	67/100	79/100
82	21617	Centreville	MD	67/100	89/100
83	21620	Chestertown	MD	67/100	84/100
84	21643	Hurlock	MD	67/100	92/100
85	21654	Oxford	MD	67/100	79/100
86	21655	Preston	MD	67/100	89/100
87	21713	Boonsboro	MD	67/100	69/100

Methodology

Water system reliability scores (0-100) combine violation frequency, violation recency, resolution rate, and system size. Systems with repeated health-based violations and unresolved issues score lowest. The reliability score focuses specifically on the water utility performance, distinct from the broader Home Safety Score.

Data sources: EPA Safe Drinking Water Information System (SDWIS), FEMA National Flood Insurance Program, EPA radon zone maps, EIA electricity rates, and Consumer Confidence Reports. Last updated: 2026-04-13.

Frequently Asked Questions

What does a low water reliability score mean?

A low reliability score (below 50) indicates a water system with frequent violations, poor resolution rates, or recurring compliance issues. These systems may have aging infrastructure, inadequate treatment, or management challenges.

How is reliability different from safety score?

The reliability score focuses specifically on the water utility performance (violations, resolution, compliance). The Home Safety Score is broader, also including lead risk, radon, and flood data. A ZIP code can have a reliable water system but still have high radon or flood risk.