Least Reliable Water Systems in Washington

Out of 726 ZIP codes with data in Washington, these are the lowest-ranked areas for reliability score. See also: National Least Reliable Water Systems in America | All Washington Rankings

Statistic	Value
ZIP codes ranked	726
Lowest value	15/100
Median value	75/100
State	Washington

100 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Reliability Score	Safety Score
1	98250	Friday Harbor	WA	15/100	70/100
2	98243	Deer Harbor	WA	18/100	66/100
3	99336	Kennewick	WA	20/100	58/100
4	99337	Kennewick	WA	20/100	58/100
5	99338	Kennewick	WA	20/100	58/100
6	98277	Oak Harbor	WA	25/100	66/100
7	98278	Oak Harbor	WA	25/100	71/100
8	98582	Salkum	WA	30/100	62/100
9	98595	Westport	WA	33/100	74/100
10	98224	Baring	WA	35/100	73/100
11	98832	Marlin	WA	35/100	78/100
12	98262	Lummi Island	WA	38/100	85/100
13	98672	White Salmon	WA	39/100	78/100
14	99114	Colville	WA	40/100	56/100
15	99118	Curlew	WA	40/100	48/100
16	99323	Burbank	WA	40/100	71/100
17	98941	Roslyn	WA	42/100	72/100
18	99003	Chattaroy	WA	42/100	69/100
19	98930	Grandview	WA	44/100	81/100
20	98266	Maple Falls	WA	45/100	91/100
21	98272	Monroe	WA	45/100	69/100
22	98565	Napavine	WA	45/100	95/100
23	99157	Northport	WA	45/100	64/100
24	99344	Othello	WA	45/100	72/100
25	98816	Chelan	WA	47/100	91/100
26	99343	Mesa	WA	47/100	62/100
27	98572	Pe Ell	WA	49/100	90/100
28	98027	Issaquah	WA	50/100	74/100
29	98029	Issaquah	WA	50/100	89/100
30	98068	Snoqualmie Pass	WA	50/100	81/100
31	98802	East Wenatchee	WA	50/100	73/100
32	98849	Riverside	WA	50/100	59/100
33	98951	Wapato	WA	50/100	67/100
34	99020	Marshall	WA	50/100	54/100
35	99156	Newport	WA	50/100	51/100
36	99371	Washtucna	WA	50/100	75/100
37	98245	Eastsound	WA	52/100	93/100
38	98264	Lynden	WA	52/100	89/100
39	99349	Mattawa	WA	52/100	82/100
40	98001	Auburn	WA	55/100	84/100
41	98002	Auburn	WA	55/100	84/100
42	98071	Auburn	WA	55/100	93/100
43	98092	Auburn	WA	55/100	84/100
44	98253	Greenbank	WA	55/100	85/100
45	98256	Index	WA	55/100	82/100
46	98260	Langley	WA	55/100	80/100
47	98325	Chimacum	WA	55/100	96/100
48	98365	Port Ludlow	WA	55/100	87/100
49	98381	Sekiu	WA	55/100	93/100
50	98520	Aberdeen	WA	55/100	71/100
51	98532	Chehalis	WA	55/100	75/100
52	98831	Manson	WA	55/100	88/100
53	98848	Quincy	WA	55/100	75/100
54	98857	Warden	WA	55/100	78/100
55	98940	Ronald	WA	55/100	77/100
56	98948	Toppenish	WA	55/100	73/100
57	99029	Reardan	WA	55/100	79/100
58	99031	Spangle	WA	55/100	67/100
59	99032	Sprague	WA	55/100	77/100
60	99111	Colfax	WA	55/100	78/100
61	99119	Cusick	WA	55/100	60/100
62	99143	Lacrosse	WA	55/100	72/100
63	99180	Usk	WA	55/100	61/100
64	99335	Kahlotus	WA	55/100	79/100
65	99353	West Richland	WA	55/100	72/100
66	99301	Pasco	WA	56/100	80/100
67	99302	Pasco	WA	56/100	79/100
68	98239	Coupeville	WA	57/100	94/100
69	98236	Clinton	WA	58/100	71/100
70	98511	Tumwater	WA	58/100	77/100
71	98623	Husum	WA	58/100	78/100
72	99161	Palouse	WA	58/100	81/100
73	98241	Darrington	WA	60/100	85/100
74	98247	Everson	WA	60/100	78/100
75	98257	La Conner	WA	60/100	88/100
76	98290	Snohomish	WA	60/100	77/100
77	98291	Snohomish	WA	60/100	92/100
78	98296	Snohomish	WA	60/100	82/100
79	98356	Morton	WA	60/100	87/100
80	98360	Orting	WA	60/100	83/100
81	98362	Port Angeles	WA	60/100	86/100
82	98363	Port Angeles	WA	60/100	91/100
83	98370	Poulsbo	WA	60/100	88/100
84	98396	Wilkeson	WA	60/100	92/100
85	98563	Montesano	WA	60/100	81/100
86	98823	Ephrata	WA	60/100	70/100
87	98826	Leavenworth	WA	60/100	81/100
88	98846	Pateros	WA	60/100	67/100
89	98850	Rock Island	WA	60/100	79/100
90	98862	Winthrop	WA	60/100	64/100
91	98922	Cle Elum	WA	60/100	49/100
92	98933	Harrah	WA	60/100	79/100
93	98936	Moxee	WA	60/100	80/100
94	98937	Naches	WA	60/100	71/100
95	99033	Tekoa	WA	60/100	79/100
96	99115	Coulee City	WA	60/100	79/100
97	99148	Loon Lake	WA	60/100	67/100
98	99179	Uniontown	WA	60/100	81/100
99	99326	Connell	WA	60/100	81/100
100	99362	Walla Walla	WA	60/100	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.

Least Reliable Water Systems in Washington — 2026

100 Lowest-Ranked ZIP Codes

Methodology

Frequently Asked Questions

What does a low water reliability score mean?

How is reliability different from safety score?

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