Water Hardness in Washington
Across 191 measured cities — with 180 more covered by labeled county-level estimates — Washington's median tap water hardness is 39.4 mg/L (2.3 gpg): soft on the USGS scale. Below: every covered city, the state's hardest and softest water, and the geology that explains it.
Data updated September 13, 2026. Sources: utility-reported water quality data and USGS/EPA Water Quality Portal samples.
What it costs to soften Washington water
Water softener cost in Washington at 2.3 gpg prices the equipment and the installation labour against the plumber wages published for Washington, and labels every range as modelled or measured rather than leaving you to guess which it is.
Washington · 2.3 grains per gallon
$994–$1,344
installed, midpoint $1,150 — a 24,000-grain unit, the size 4 people at this hardness need.
Salt and drain water over 10 years: $445–$1,040 — the 2,518,500 grains of hardness this household removes, at the national salt price and water rate whose sources are named below. Filter changes and Service contract are omitted rather than assumed.
Sized for 4 people regenerating every 7 days: 4,830 grains of capacity needed, rounded up to the next common residential size. The median of 191 measured Washington cities in our hardness dataset. Modelled: the standard build band published for that state at the size this hardness calls for, equipment priced 2026-10-04 against the May 2025 reference period (OEWS M2025). Salt: the median retailer price of 3 retailers, read 2026-10-04, at a declared salt dose per regeneration. Drain water: about 50 gallons per regeneration from a government extension estimate read 2026-10-04, at the 2024 national average water and sewer rate from a government source read 2026-10-04.
Deciding whether it is worth it at all? Start from how much a water softener costs nationally — the same equipment, installation and ten-year ownership breakdown before any state wage adjustment is applied.
Washington Cities by Hardness Category
Measured cities only — labeled county estimates never enter the category counts or the median.
| Category | Range | Measured cities | Share |
|---|---|---|---|
| Soft | 0-60 mg/L | 125 | 65.4% |
| Moderately hard | 60-120 mg/L | 53 | 27.7% |
| Hard | 120-180 mg/L | 9 | 4.7% |
| Very hard | >180 mg/L | 4 | 2.1% |
Hardest and Softest Water in Washington
Measured values only; labeled county estimates and values under active dispute never rank.
Hardest water in Washington
- Omak — 289.1 mg/L (16.9 gpg), very hard
- Pateros — 281.3 mg/L (16.4 gpg), very hard
- Tonasket — 235.7 mg/L (13.8 gpg), very hard
- Grandview — 208.2 mg/L (12.2 gpg), very hard
- Marrowstone — 157.0 mg/L (9.2 gpg), hard
Softest water in Washington
- Alderwood Manor — 12.6 mg/L (0.7 gpg), soft
- Bothell East — 12.6 mg/L (0.7 gpg), soft
- Bothell West — 12.6 mg/L (0.7 gpg), soft
- Brier — 12.6 mg/L (0.7 gpg), soft
- Clearview — 12.6 mg/L (0.7 gpg), soft
Every Covered City in Washington
All 371 covered Washington cities, sorted by population served. "County estimate" rows are labeled context values from USGS/EPA Water Quality Portal county sampling — they never enter the median above. City names link to each city's full water quality page.
| City | Hardness (mg/L) | gpg | Category | Data |
|---|---|---|---|---|
| Boulevard Park | 30.9 | 1.8 | Soft | Utility-reported |
| Bryn Mawr-Skyway | 30.9 | 1.8 | Soft | Utility-reported |
| Burien | 30.9 | 1.8 | Soft | Utility-reported |
| Seattle | 30.9 | 1.8 | Soft | Utility-reported |
| Shoreline | 30.9 | 1.8 | Soft | Utility-reported |
| White Center | 30.9 | 1.8 | Soft | Utility-reported |
| Five Corners | 105.0 | 6.1 | Moderately hard | Utility-reported |
| Hazel Dell | 105.0 | 6.1 | Moderately hard | Utility-reported |
| Hockinson | 105.0 | 6.1 | Moderately hard | Utility-reported |
| Minnehaha | 105.0 | 6.1 | Moderately hard | Utility-reported |
| Orchards | 105.0 | 6.1 | Moderately hard | Utility-reported |
| Vancouver | 105.0 | 6.1 | Moderately hard | Utility-reported |
| Alderton | 21.8 | 1.3 | Soft | Utility-reported |
| Browns Point | 21.8 | 1.3 | Soft | Utility-reported |
| Clover Creek | 21.8 | 1.3 | Soft | Utility-reported |
| Dash Point | 21.8 | 1.3 | Soft | Utility-reported |
| Fife Heights | 21.8 | 1.3 | Soft | Utility-reported |
| Frederickson | 21.8 | 1.3 | Soft | Utility-reported |
| Graham | 21.8 | 1.3 | Soft | Utility-reported |
| McMillin | 21.8 | 1.3 | Soft | Utility-reported |
| Midland | 21.8 | 1.3 | Soft | Utility-reported |
| Prairie Heights | 21.8 | 1.3 | Soft | Utility-reported |
| Prairie Ridge | 21.8 | 1.3 | Soft | Utility-reported |
| Ruston | 21.8 | 1.3 | Soft | Utility-reported |
| South Hill | 21.8 | 1.3 | Soft | Utility-reported |
| Summit View | 21.8 | 1.3 | Soft | Utility-reported |
| Tacoma | 21.8 | 1.3 | Soft | Utility-reported |
| Tehaleh | 21.8 | 1.3 | Soft | Utility-reported |
| University Place | 21.8 | 1.3 | Soft | Utility-reported |
| Waller | 21.8 | 1.3 | Soft | Utility-reported |
| Beaux Arts Village | 34.9 | 2.0 | Soft | Utility-reported |
| Bellevue | 34.9 | 2.0 | Soft | Utility-reported |
| Clyde Hill | 34.9 | 2.0 | Soft | Utility-reported |
| Hunts Point | 34.9 | 2.0 | Soft | Utility-reported |
| Medina | 34.9 | 2.0 | Soft | Utility-reported |
| Yarrow Point | 34.9 | 2.0 | Soft | Utility-reported |
| Spokane | 22.9 | 1.3 | Soft | County estimate |
| Alderwood Manor | 12.6 | 0.7 | Soft | Utility-reported |
| Bothell East | 12.6 | 0.7 | Soft | Utility-reported |
| Bothell West | 12.6 | 0.7 | Soft | Utility-reported |
| Brier | 12.6 | 0.7 | Soft | Utility-reported |
| Clearview | 12.6 | 0.7 | Soft | Utility-reported |
| Lake Stickney | 12.6 | 0.7 | Soft | Utility-reported |
| Larch Way | 12.6 | 0.7 | Soft | Utility-reported |
| Maltby | 12.6 | 0.7 | Soft | Utility-reported |
| Martha Lake | 12.6 | 0.7 | Soft | Utility-reported |
| Meadowdale | 12.6 | 0.7 | Soft | Utility-reported |
| Mill Creek | 12.6 | 0.7 | Soft | Utility-reported |
| Mill Creek East | 12.6 | 0.7 | Soft | Utility-reported |
| North Lynnwood | 12.6 | 0.7 | Soft | Utility-reported |
| Picnic Point | 12.6 | 0.7 | Soft | Utility-reported |
| Eastmont | 18.9 | 1.1 | Soft | Utility-reported |
| Everett | 18.9 | 1.1 | Soft | Utility-reported |
| Redmond | 53.0 | 3.1 | Soft | Utility-reported |
| Union Hill-Novelty Hill | 53.0 | 3.1 | Soft | Utility-reported |
| Des Moines | 37.9 | 2.2 | Soft | Utility-reported |
| Federal Way | 37.9 | 2.2 | Soft | Utility-reported |
| Lakeland North | 37.9 | 2.2 | Soft | Utility-reported |
| Lakeland South | 37.9 | 2.2 | Soft | Utility-reported |
| Amboy | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Barberton | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Brush Prairie | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Cherry Grove | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Dollars Corner | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Duluth | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Felida | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Fern Prairie | 85.9 | 5.0 | Moderately hard | Utility-reported |
| La Center | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Lake Shore | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Lewisville | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Meadow Glade | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Mount Vista | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Salmon Creek | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Venersborg | 85.9 | 5.0 | Moderately hard | Utility-reported |
| Kenmore | 25.1 | 1.5 | Soft | Utility-reported |
| Bellingham | 29.2 | 1.7 | Soft | Utility-reported |
| Marietta-Alderwood | 29.2 | 1.7 | Soft | Utility-reported |
| Renton | 73.0 | 4.3 | Moderately hard | Utility-reported |
| Arlington | 28.6 | 1.7 | Soft | County estimate |
| Finley | 96.1 | 5.6 | Moderately hard | Utility-reported |
| Kennewick | 96.1 | 5.6 | Moderately hard | Utility-reported |
| Lacey | 110.0 | 6.4 | Moderately hard | Utility-reported |
| Tanglewilde | 110.0 | 6.4 | Moderately hard | Utility-reported |
| Pasco | 268.5 | 15.7 | Very hard | County estimate |
| DuPont | 39.3 | 2.3 | Soft | County estimate |
| Alger | 18.1 | 1.1 | Soft | Utility-reported |
| Bay View | 18.1 | 1.1 | Soft | Utility-reported |
| Big Lake | 18.1 | 1.1 | Soft | Utility-reported |
| Burlington | 18.1 | 1.1 | Soft | Utility-reported |
| Mount Vernon | 18.1 | 1.1 | Soft | Utility-reported |
| Sedro-Woolley | 18.1 | 1.1 | Soft | Utility-reported |
| Kent | 59.4 | 3.5 | Soft | Utility-reported |
| Olympia | 52.0 | 3.0 | Soft | Utility-reported |
| Marysville | 28.6 | 1.7 | Soft | County estimate |
| Gleed | 30.6 | 1.8 | Soft | Computed from Ca+Mg |
| Yakima | 30.6 | 1.8 | Soft | Computed from Ca+Mg |
| Bremerton | 38.9 | 2.3 | Soft | Utility-reported |
| Enetai | 38.9 | 2.3 | Soft | Utility-reported |
| Gorst | 38.9 | 2.3 | Soft | Utility-reported |
| Kitsap Lake | 38.9 | 2.3 | Soft | Utility-reported |
| Navy Yard City | 38.9 | 2.3 | Soft | Utility-reported |
| Tracyton | 38.9 | 2.3 | Soft | Utility-reported |
| Normandy Park | 64.1 | 3.8 | Moderately hard | Utility-reported |
| SeaTac | 64.1 | 3.8 | Moderately hard | Utility-reported |
| Sammamish | 62.6 | 3.7 | Moderately hard | Utility-reported |
| Kirkland | 21.3 | 1.3 | Soft | Utility-reported |
| Fairwood | 23.8 | 1.4 | Soft | Utility-reported |
| Maple Heights-Lake Desire | 23.8 | 1.4 | Soft | Utility-reported |
| Lynnwood | 24.3 | 1.4 | Soft | Utility-reported |
| Lakewood | 72.4 | 4.2 | Moderately hard | Utility-reported |
| Auburn | 57.2 | 3.4 | Soft | Utility-reported |
| Lake Morton-Berrydale | 57.2 | 3.4 | Soft | Utility-reported |
| Tumwater | 60.2 | 3.5 | Moderately hard | Utility-reported |
| Spanaway | 39.3 | 2.3 | Soft | County estimate |
| Cottage Lake | 25.3 | 1.5 | Soft | Utility-reported |
| Woodinville | 25.3 | 1.5 | Soft | Utility-reported |
| Richland | 89.2 | 5.2 | Moderately hard | Utility-reported |
| Arlington Heights | 35.8 | 2.1 | Soft | Utility-reported |
| Bunk Foss | 35.8 | 2.1 | Soft | Utility-reported |
| Canyon Creek | 35.8 | 2.1 | Soft | Utility-reported |
| Cavalero | 35.8 | 2.1 | Soft | Utility-reported |
| Chain Lake | 35.8 | 2.1 | Soft | Utility-reported |
| Lake Bosworth | 35.8 | 2.1 | Soft | Utility-reported |
| Lake Roesiger | 35.8 | 2.1 | Soft | Utility-reported |
| Lake Stevens | 35.8 | 2.1 | Soft | Utility-reported |
| Lochsloy | 35.8 | 2.1 | Soft | Utility-reported |
| Machias | 35.8 | 2.1 | Soft | Utility-reported |
| McChord AFB | 39.3 | 2.3 | Soft | County estimate |
| Roy | 39.3 | 2.3 | Soft | County estimate |
| Covington | 45.9 | 2.7 | Soft | Utility-reported |
| Lake Holm | 45.9 | 2.7 | Soft | Utility-reported |
| Maple Valley | 45.9 | 2.7 | Soft | Utility-reported |
| Ravensdale | 45.9 | 2.7 | Soft | Utility-reported |
| Shadow Lake | 45.9 | 2.7 | Soft | Utility-reported |
| Longview | 127.0 | 7.4 | Hard | Utility-reported |
| Longview Heights | 127.0 | 7.4 | Hard | Utility-reported |
| Edmonds | 15.6 | 0.9 | Soft | Utility-reported |
| Liberty Lake | 22.9 | 1.3 | Soft | County estimate |
| Chehalis | 2.4 | 0.1 | Soft | County estimate |
| Issaquah | 44.1 | 2.6 | Soft | Utility-reported |
| Bonney Lake | 95.3 | 5.6 | Moderately hard | Utility-reported |
| Lake Tapps | 95.3 | 5.6 | Moderately hard | Utility-reported |
| Clarkston | 96.0 | 5.6 | Moderately hard | County estimate |
| Walla Walla | 38.8 | 2.3 | Soft | County estimate |
| North Puyallup | 93.2 | 5.5 | Moderately hard | Utility-reported |
| Puyallup | 93.2 | 5.5 | Moderately hard | Utility-reported |
| Ahtanum | 56.7 | 3.3 | Soft | Computed from Ca+Mg |
| Summitview | 56.7 | 3.3 | Soft | Computed from Ca+Mg |
| Camas | 39.4 | 2.3 | Soft | Utility-reported |
| South Wenatchee | 80.4 | 4.7 | Moderately hard | Utility-reported |
| Wenatchee | 80.4 | 4.7 | Moderately hard | Utility-reported |
| Bothell | 30.5 | 1.8 | Soft | Utility-reported |
| Greenacres | 22.9 | 1.3 | Soft | County estimate |
| Pullman | 115.0 | 6.7 | Moderately hard | Computed from Ca+Mg |
| Battle Ground | 83.1 | 4.9 | Moderately hard | Utility-reported |
| Manchester | 85.8 | 5.0 | Moderately hard | County estimate |
| Hobart | 62.7 | 3.7 | Moderately hard | County estimate |
| Centralia | 2.4 | 0.1 | Soft | County estimate |
| Country Homes | 124.0 | 7.3 | Hard | Utility-reported |
| Green Bluff | 124.0 | 7.3 | Hard | Utility-reported |
| Mead | 124.0 | 7.3 | Hard | Utility-reported |
| East Wenatchee | 71.3 | 4.2 | Moderately hard | County estimate |
| Mountlake Terrace | 14.3 | 0.8 | Soft | Utility-reported |
| Shelton | 38.6 | 2.3 | Soft | County estimate |
| Silverdale | 85.8 | 5.0 | Moderately hard | County estimate |
| Mercer Island | 39.4 | 2.3 | Soft | Utility-reported |
| Asotin | 96.0 | 5.6 | Moderately hard | County estimate |
| Mukilteo | 28.6 | 1.7 | Soft | County estimate |
| Sequim | 50.6 | 3.0 | Soft | County estimate |
| Oak Harbor | 44.8 | 2.6 | Soft | Utility-reported |
| Cathcart | 43.3 | 2.5 | Soft | Utility-reported |
| Fobes Hill | 43.3 | 2.5 | Soft | Utility-reported |
| High Bridge | 43.3 | 2.5 | Soft | Utility-reported |
| Silver Firs | 43.3 | 2.5 | Soft | Utility-reported |
| Lynden | 35.7 | 2.1 | Soft | County estimate |
| Washougal | 41.4 | 2.4 | Soft | Utility-reported |
| Ellensburg | 59.5 | 3.5 | Soft | Utility-reported |
| East Renton Highlands | 30.0 | 1.8 | Soft | Utility-reported |
| Ridgefield | 59.4 | 3.5 | Soft | County estimate |
| Aberdeen | 22.7 | 1.3 | Soft | County estimate |
| West Richland | 33.1 | 1.9 | Soft | Utility-reported |
| Poulsbo | 66.6 | 3.9 | Moderately hard | Utility-reported |
| Enumclaw | 61.6 | 3.6 | Moderately hard | Utility-reported |
| Sunnyside | 74.8 | 4.4 | Moderately hard | County estimate |
| Port Townsend | 59.9 | 3.5 | Soft | Utility-reported |
| Esperance | 86.1 | 5.0 | Moderately hard | Utility-reported |
| Woodway | 86.1 | 5.0 | Moderately hard | Utility-reported |
| Snoqualime | 41.4 | 2.4 | Soft | Utility-reported |
| Snoqualmie | 41.4 | 2.4 | Soft | Utility-reported |
| Yelm | 52.5 | 3.1 | Soft | County estimate |
| Sunnyslope | 80.0 | 4.7 | Moderately hard | Utility-reported |
| Hansville | 90.4 | 5.3 | Moderately hard | Utility-reported |
| Indianola | 90.4 | 5.3 | Moderately hard | Utility-reported |
| Kingston | 90.4 | 5.3 | Moderately hard | Utility-reported |
| Port Gamble Tribal Community | 90.4 | 5.3 | Moderately hard | Utility-reported |
| Sumner | 39.3 | 2.3 | Soft | County estimate |
| Kelso | 15.6 | 0.9 | Soft | County estimate |
| Cheney | 22.9 | 1.3 | Soft | County estimate |
| Port Orchard | 85.8 | 5.0 | Moderately hard | County estimate |
| Newcastle | 27.4 | 1.6 | Soft | Utility-reported |
| Selah | 146.7 | 8.6 | Hard | Computed from Ca+Mg |
| Bainbridge Island | 54.8 | 3.2 | Soft | Utility-reported |
| Stanwood | 28.6 | 1.7 | Soft | County estimate |
| Hoquiam | 22.7 | 1.3 | Soft | County estimate |
| Gig Harbor | 45.9 | 2.7 | Soft | Utility-reported |
| Rosedale | 45.9 | 2.7 | Soft | Utility-reported |
| Wollochet | 45.9 | 2.7 | Soft | Utility-reported |
| Snohomish | 28.6 | 1.7 | Soft | County estimate |
| Grandview | 208.2 | 12.2 | Very hard | Computed from Ca+Mg |
| Raymond | 15.6 | 0.9 | Soft | County estimate |
| Woodland | 15.6 | 0.9 | Soft | County estimate |
| Ocean Park | 15.6 | 0.9 | Soft | County estimate |
| Leavenworth | 14.7 | 0.9 | Soft | County estimate |
| Orting | 39.3 | 2.3 | Soft | County estimate |
| Marrowstone | 157.0 | 9.2 | Hard | Utility-reported |
| Port Hadlock-Irondale | 157.0 | 9.2 | Hard | Utility-reported |
| Duvall | 21.0 | 1.2 | Soft | Utility-reported |
| Buckley | 39.3 | 2.3 | Soft | County estimate |
| Airway Heights | 22.9 | 1.3 | Soft | County estimate |
| Chelan | 21.4 | 1.3 | Soft | Computed from Ca+Mg |
| Ocean Shores | 22.7 | 1.3 | Soft | County estimate |
| Toppenish | 62.8 | 3.7 | Moderately hard | Computed from Ca+Mg |
| Othello | 33.2 | 1.9 | Soft | Computed from Ca+Mg |
| Ephrata | 168.0 | 9.8 | Hard | County estimate |
| North Bend | 62.7 | 3.7 | Moderately hard | County estimate |
| Steilacoom | 39.3 | 2.3 | Soft | County estimate |
| Milton | 39.3 | 2.3 | Soft | County estimate |
| Terrace Heights | 88.1 | 5.2 | Moderately hard | Computed from Ca+Mg |
| Kalama | 15.6 | 0.9 | Soft | County estimate |
| Vashon | 62.7 | 3.7 | Moderately hard | County estimate |
| Pacific | 56.2 | 3.3 | Soft | Utility-reported |
| Manson | 14.7 | 0.9 | Soft | County estimate |
| Prosser | 74.8 | 4.4 | Moderately hard | County estimate |
| Benton City | 74.8 | 4.4 | Moderately hard | County estimate |
| Cashmere | 14.7 | 0.9 | Soft | County estimate |
| Montesano | 22.7 | 1.3 | Soft | County estimate |
| Medical Lake | 22.9 | 1.3 | Soft | County estimate |
| Cle Elum | 44.1 | 2.6 | Soft | County estimate |
| Mattawa | 168.0 | 9.8 | Hard | County estimate |
| Granite Falls | 28.6 | 1.7 | Soft | County estimate |
| Grayland | 15.6 | 0.9 | Soft | County estimate |
| Westport | 22.7 | 1.3 | Soft | County estimate |
| Belfair | 38.6 | 2.3 | Soft | County estimate |
| Eastsound | 163.0 | 9.5 | Hard | County estimate |
| Omak | 289.1 | 16.9 | Very hard | Computed from Ca+Mg |
| Newport | 70.5 | 4.1 | Moderately hard | County estimate |
| Dallesport | 63.5 | 3.7 | Moderately hard | County estimate |
| Castle Rock | 15.6 | 0.9 | Soft | County estimate |
| Brewster | 117.0 | 6.8 | Moderately hard | County estimate |
| Suquamish | 85.8 | 5.0 | Moderately hard | County estimate |
| Coupeville | 289.0 | 16.9 | Very hard | County estimate |
| Ilwaco | 15.6 | 0.9 | Soft | County estimate |
| Granger | 166.0 | 9.7 | Hard | County estimate |
| White Salmon | 63.5 | 3.7 | Moderately hard | County estimate |
| Hoodsport | 38.6 | 2.3 | Soft | County estimate |
| Napavine | 2.4 | 0.1 | Soft | County estimate |
| Fox Island | 39.3 | 2.3 | Soft | County estimate |
| Rochester | 52.5 | 3.1 | Soft | County estimate |
| Everson | 35.7 | 2.1 | Soft | County estimate |
| Nooksack | 35.7 | 2.1 | Soft | County estimate |
| Eatonville | 39.3 | 2.3 | Soft | County estimate |
| Colfax | 114.0 | 6.7 | Moderately hard | County estimate |
| Monroe | 28.6 | 1.7 | Soft | County estimate |
| Tenino | 52.5 | 3.1 | Soft | County estimate |
| Friday Harbor | 163.0 | 9.5 | Hard | County estimate |
| Zillah | 166.0 | 9.7 | Hard | County estimate |
| Naches | 166.0 | 9.7 | Hard | County estimate |
| Royal City | 168.0 | 9.8 | Hard | County estimate |
| Dayton | 92.4 | 5.4 | Moderately hard | Computed from Ca+Mg |
| Oroville | 117.0 | 6.8 | Moderately hard | County estimate |
| Fall City | 62.7 | 3.7 | Moderately hard | County estimate |
| Okanogan | 117.0 | 6.8 | Moderately hard | County estimate |
| Port Ludlow | 69.3 | 4.0 | Moderately hard | Utility-reported |
| Yacolt | 59.4 | 3.5 | Soft | County estimate |
| South Bend | 15.6 | 0.9 | Soft | County estimate |
| Winlock | 2.4 | 0.1 | Soft | County estimate |
| Rainier | 52.5 | 3.1 | Soft | County estimate |
| Mccleary | 22.7 | 1.3 | Soft | County estimate |
| Kettle Falls | 110.0 | 6.4 | Moderately hard | County estimate |
| Chewelah | 74.4 | 4.3 | Moderately hard | County estimate |
| Rock Island | 71.3 | 4.2 | Moderately hard | County estimate |
| Black Diamond | 62.7 | 3.7 | Moderately hard | County estimate |
| Carnation | 62.7 | 3.7 | Moderately hard | County estimate |
| Tonasket | 235.7 | 13.8 | Very hard | Computed from Ca+Mg |
| Mabton | 166.0 | 9.7 | Hard | County estimate |
| Stevenson | 37.5 | 2.2 | Soft | Computed from Ca+Mg |
| Kittitas | 44.1 | 2.6 | Soft | County estimate |
| Morton | 2.4 | 0.1 | Soft | County estimate |
| Darrington | 28.6 | 1.7 | Soft | County estimate |
| Allyn | 38.6 | 2.3 | Soft | County estimate |
| Roslyn | 44.1 | 2.6 | Soft | County estimate |
| Electric City | 168.0 | 9.8 | Hard | County estimate |
| Toledo | 2.4 | 0.1 | Soft | County estimate |
| Onalaska | 2.4 | 0.1 | Soft | County estimate |
| Clinton | 289.0 | 16.9 | Very hard | County estimate |
| Cosmopolis | 22.7 | 1.3 | Soft | County estimate |
| Waitsburg | 38.8 | 2.3 | Soft | County estimate |
| Newman Lake | 22.9 | 1.3 | Soft | County estimate |
| Bingen | 61.6 | 3.6 | Moderately hard | County estimate |
| Sumas | 35.7 | 2.1 | Soft | County estimate |
| Entiat | 14.7 | 0.9 | Soft | County estimate |
| Ritzville | 251.0 | 14.7 | Very hard | County estimate |
| Davenport | 149.0 | 8.7 | Hard | County estimate |
| Republic | 110.0 | 6.4 | Moderately hard | County estimate |
| Cathlamet | 56.6 | 3.3 | Soft | County estimate |
| Taholah | 22.7 | 1.3 | Soft | County estimate |
| La Conner | 9.0 | 0.5 | Soft | County estimate |
| Mossyrock | 2.4 | 0.1 | Soft | County estimate |
| Bow | 9.0 | 0.5 | Soft | County estimate |
| Pomeroy | 114.5 | 6.7 | Moderately hard | County estimate |
| Point Roberts | 35.7 | 2.1 | Soft | County estimate |
| Grand Coulee | 71.3 | 4.2 | Moderately hard | County estimate |
| Langley | 289.0 | 16.9 | Very hard | County estimate |
| Anderson Island | 39.3 | 2.3 | Soft | County estimate |
| Coulee Dam | 117.0 | 6.8 | Moderately hard | County estimate |
| Pacific Beach | 22.7 | 1.3 | Soft | County estimate |
| Oakville | 22.7 | 1.3 | Soft | County estimate |
| Harrah | 166.0 | 9.7 | Hard | County estimate |
| Neah Bay | 50.6 | 3.0 | Soft | County estimate |
| Palouse | 114.0 | 6.7 | Moderately hard | County estimate |
| Pateros | 281.3 | 16.4 | Very hard | Computed from Ca+Mg |
| Waterville | 71.3 | 4.2 | Moderately hard | County estimate |
| Camano Island | 289.0 | 16.9 | Very hard | County estimate |
| Ashford | 39.3 | 2.3 | Soft | County estimate |
| Wilkeson | 39.3 | 2.3 | Soft | County estimate |
| North Bonneville | 61.6 | 3.6 | Moderately hard | County estimate |
| Tekoa | 114.0 | 6.7 | Moderately hard | County estimate |
| George | 149.6 | 8.8 | Hard | Computed from Ca+Mg |
| Twisp | 117.0 | 6.8 | Moderately hard | County estimate |
| Chimacum | 25.4 | 1.5 | Soft | County estimate |
| Union | 38.6 | 2.3 | Soft | County estimate |
| Quinault | 22.7 | 1.3 | Soft | County estimate |
| Vader | 2.4 | 0.1 | Soft | County estimate |
| Buena | 166.0 | 9.7 | Hard | County estimate |
| St. John | 114.0 | 6.7 | Moderately hard | County estimate |
| Tokeland | 15.6 | 0.9 | Soft | County estimate |
| Cusick | 70.5 | 4.1 | Moderately hard | County estimate |
| Malott | 117.0 | 6.8 | Moderately hard | County estimate |
| Malaga | 14.7 | 0.9 | Soft | County estimate |
| Colton | 114.0 | 6.7 | Moderately hard | County estimate |
| Albion | 114.0 | 6.7 | Moderately hard | County estimate |
| Bucoda | 52.5 | 3.1 | Soft | County estimate |
| Marshall | 22.9 | 1.3 | Soft | County estimate |
| South Cle Elum | 19.5 | 1.1 | Soft | Computed from Ca+Mg |
| Prescott | 38.8 | 2.3 | Soft | County estimate |
| Oakesdale | 114.0 | 6.7 | Moderately hard | County estimate |
| Carson | 61.6 | 3.6 | Moderately hard | County estimate |
| Four Lakes | 22.9 | 1.3 | Soft | County estimate |
| Riverside | 117.0 | 6.8 | Moderately hard | County estimate |
| Ronald | 44.1 | 2.6 | Soft | County estimate |
| Moses Lake | 168.0 | 9.8 | Hard | County estimate |
| Uniontown | 114.0 | 6.7 | Moderately hard | County estimate |
| Ferndale | 35.7 | 2.1 | Soft | County estimate |
| Usk | 70.5 | 4.1 | Moderately hard | County estimate |
| Quincy | 168.0 | 9.8 | Hard | County estimate |
| Wapato | 166.0 | 9.7 | Hard | County estimate |
| Peshastin | 14.7 | 0.9 | Soft | County estimate |
| Orondo | 71.3 | 4.2 | Moderately hard | County estimate |
| Nespelem | 117.0 | 6.8 | Moderately hard | County estimate |
| Grapeview | 38.6 | 2.3 | Soft | County estimate |
| Port Angeles | 50.6 | 3.0 | Soft | County estimate |
| Freeland | 289.0 | 16.9 | Very hard | County estimate |
| Bridgeport | 71.3 | 4.2 | Moderately hard | County estimate |
| Lind | 251.0 | 14.7 | Very hard | County estimate |
| Lopez Island | 163.0 | 9.5 | Hard | County estimate |
| Maple Falls | 35.7 | 2.1 | Soft | County estimate |
| Mesa | 268.5 | 15.7 | Very hard | County estimate |
| Packwood | 2.4 | 0.1 | Soft | County estimate |
| Trout Lake | 63.5 | 3.7 | Moderately hard | County estimate |
| Waverly | 22.9 | 1.3 | Soft | County estimate |
| Winthrop | 117.0 | 6.8 | Moderately hard | County estimate |
Above 120 mg/L (7 gpg), scale is usually worth treating — see our water softener guide, or size a system with the hardness calculator & converter.
The Geology Behind Washington's Water Hardness
Washington sits in the Pacific maritime volcanic terrain region.
The Pacific Northwest, Alaska, and Hawaii share young volcanic bedrock - basalt and other igneous rock with little carbonate to dissolve - and most supplies come from heavy rainfall, snowmelt, or fast-recharging volcanic aquifers. Water simply does not stay in contact with soluble carbonate long enough to harden. That is why the USGS maps these states among the softest in the nation.
Washington Water Hardness FAQ
Does Washington have hard water?
On the whole, no — Washington's statewide median sits below the hard threshold, though some cities run harder. The median is 39.4 mg/L (2.3 gpg) — soft on the USGS scale, where anything above 120 mg/L (7 gpg) counts as hard. 13 of Washington's 191 measured cities fall in the hard or very hard bands (7%), so check your own city rather than the state average.
How hard is tap water in Washington?
Across the 191 Washington cities with measured values in our index, the median hardness is 39.4 mg/L (2.3 gpg) — soft on the USGS scale. Individual cities range from 12.6 to 289.1 mg/L, so check your own city rather than assuming the state number.
Which city in Washington has the hardest water?
Omak has the hardest measured tap water in our Washington index at 289.1 mg/L (16.9 gpg) — very hard on the USGS scale. Rankings use measured utility values only; labeled county estimates and values under active dispute are excluded.
Do I need a water softener in Washington?
13 of Washington's 191 measured cities (7%) fall in the hard or very hard bands — above 120 mg/L (7 gpg), the level where most water treatment professionals suggest considering an ion-exchange softener. Hardness varies utility to utility, so look up your own city's value before sizing equipment.
How do I find my city's exact water hardness?
Enter your ZIP code in our free lookup at tapwaterdata.com/zip to see the value we hold for your Washington city from utility-reported water quality data, check your water utility's annual Consumer Confidence Report (CCR), or use a home test-strip kit.
Need whole-house or professional water treatment?
For the problems a pitcher or under-sink filter cannot fix — scale, rust and black staining, sulfur smell, well contamination, or test results you cannot explain. Tell us what is happening and we will connect you with a local water-treatment professional.
Get the Weekly Water Brief
One email a week on water testing, treatment, and what water-quality data means for your home.
One email a week. Unsubscribe anytime.