Spokane, WA water hardness
City of Spokane Water Department publishes an average hardness of 159 mg/L for its system, in its City of Spokane Water Department 2025 Technical Drinking Water Report (Appendix III, Drinking Water Inorganics Summary). On the USGS scale that is hard water, though the utility's own range crosses more than one class — it spans moderately hard, hard and very hard water from end to end.
Every figure City of Spokane Water Department publishes, by source
The utility publishes a system average, shown above, and separately the figure for each source behind it. Which source serves an address determines which of these rows describes its water.
| Source as published | mg/L (ppm) | Grains per gallon | USGS class |
|---|---|---|---|
| Central well station (29-Jul-2025) | 127 | 7.4 | Hard |
| Electric well station (29-Jul-2025) | 133 | 7.8 | Hard |
| Grace well station (25-Jul-2023) | 90.6 | 5.3 | Moderately hard |
| Havana well station (27-Aug-2024) | 360 | 21.1 | Very hard |
| Hoffman well station (25-Jul-2023) | 136 | 8 | Hard |
| Nevada well station (27-Aug-2024) | 102 | 6 | Moderately hard |
| Parkwater well station (27-Aug-2024) | 163 | 9.5 | Hard |
| Ray well station (27-Aug-2024) | 159 | 9.3 | Hard |
Figures in the grains column are the utility's own where it published them. Where it published only one unit, the other column is our conversion at 17.1 mg/L per grain, and the row above says which. Nothing in this table is averaged across well stations.
The published figures, exactly as they appear
This is the hardness line transcribed from the source, with nothing added:
WELL STATION CENTRAL ELECTRIC GRACE HAVANA HOFFMAN NEVADA PARKWATER RAY […] HARDNESS (as CaCO3) # 127 133 90.6 360 136 102 163 159 unregulated [CURRENT DATA SUMMARY: MEAN MAX MIN COUNT] 159 360 90.6 8 […] RESULTS ARE IN mg/L EXCEPT WHERE OTHERWISE NOTED […] # divide by 17.1 to convert to grains per gallon
City of Spokane Water Department, City of Spokane Water Department 2025 Technical Drinking Water Report (Appendix III, Drinking Water Inorganics Summary)
Units as published: mg/L (results are in mg/L except where otherwise noted). What kind of figure it is: an average with a range. Retrieved 2026-10-26.
Spokane hardness in mg/L and grains per gallon
Water-quality reports use mg/L (identical to ppm). Softener instructions and plumbing specifications use grains per gallon. Both are below. Where a figure is our arithmetic rather than the utility's own number, it says so.
| Figure | mg/L (ppm) | Grains per gallon | Whose number |
|---|---|---|---|
| Published average | 159 | 9.3 | mg/L published, gpg is our conversion |
| Low end of published range | 90.6 | 5.3 | mg/L published, gpg is our conversion |
| High end of published range | 360 | 21.1 | mg/L published, gpg is our conversion |
| Plotted on the scale above | 159 | 9.3 | published average; the gpg here is our conversion at 17.1, so it can differ slightly from a utility’s own rounded gpg figure |
The conversion, both ways: gpg = mg/L ÷ 17.1 and mg/L = gpg × 17.1. Worked for this system: 159 ÷ 17.1 = 9.3 gpg. The converter does °dH and °f as well, and why the factor is 17.1 explains where the number comes from.
What this figure does not tell you
Service area and source water
| Utility | City of Spokane Water Department |
|---|---|
| Service area as published | The City of Spokane water system, supplied by eight well stations. The report does not say which addresses each well station serves. |
| Source water | Groundwater from the Spokane Valley-Rathdrum Prairie Aquifer, pumped at eight well stations. |
Provenance of every number on this page
| Source document | City of Spokane Water Department 2025 Technical Drinking Water Report (Appendix III, Drinking Water Inorganics Summary) |
|---|---|
| Source URL | https://static.spokanecity.org/documents/publicworks/water/2025-technical-drinking-water-report-2026-05-22.pdf |
| Published by | City of Spokane Water Department |
| Report year | 2025 |
| Year note | The inorganics summary is dated 18-Mar-2026 and gives the most recent result for each well station; the sampling dates run from July 2023 to July 2025. |
| Retrieved | 2026-10-26 |
| Classification bands | USGS Water Science School, retrieved 2026-10-16 |
Notes the report forces on this page
- The 159 mg/L mean, 90.6 minimum and 360 maximum are the report's own Current Data Summary columns across the eight well stations. Each station's figure is its most recent single result, and the sampling dates differ by up to two years.
- The mean is a simple mean across stations, not weighted by how much water each pumps. The Havana station's 360 mg/L is the only figure in the very hard band; the rest run from moderately hard to hard.
- Each well station has one figure, so the table below shows it in the average column; it is a single result, not an average.
If you are sizing a softener for Spokane water
At 9.3 gpg, the sizing arithmetic starts from your household's water use, not from the hardness alone. The calculator below is pre-filled with this system's figure and every other input is an editable assumption.
Whether a softener is worth installing at this hardness is a judgement, not arithmetic, and it is not one this site makes for you. Nothing here has been tested by the author.
Where Spokane sits against other verified systems
- Portland, OR 9 mg/L 0.5 gpg Soft
- Boston, MA 16 mg/L 1 gpg Soft
- Manchester, NH 17.9 mg/L 1 gpg Soft
- Seattle, WA 19.1 mg/L 1.1 gpg Soft
- Raleigh, NC 25 mg/L 1.47 gpg Soft
- New York, NY 32 mg/L 2 gpg Soft
- Charlotte, NC 32 mg/L 1.9 gpg Soft
- Memphis, TN 46 mg/L 2.7 gpg Soft
- Norfolk, VA 48 mg/L 2.8 gpg Soft
- Anchorage, AK 56 mg/L 3.3 gpg Soft
- Virginia Beach, VA 56 mg/L 3.3 gpg Soft
- Oakland, CA 68.4 mg/L 4 gpg Moderately hard
- Nashville, TN 77.3 mg/L 4.5 gpg Moderately hard
- Sacramento, CA 83 mg/L 4.9 gpg Moderately hard
- Fresno, CA 89.3 mg/L 5.2 gpg Moderately hard
- Saint Paul, MN 90 mg/L 5 gpg Moderately hard
- Austin, TX 93 mg/L 5.4 gpg Moderately hard
- Minneapolis, MN 94 mg/L 5.5 gpg Moderately hard
- Washington, DC 95 mg/L 5.6 gpg Moderately hard
- Baltimore, MD 97.5 mg/L 5.7 gpg Moderately hard
- Birmingham, AL 98 mg/L 5.7 gpg Moderately hard
- Kansas City, MO 100 mg/L 5.8 gpg Moderately hard
- Denver, CO 105 mg/L 6.1 gpg Moderately hard
- Detroit, MI 107 mg/L 6.3 gpg Moderately hard
- Aurora, CO 113 mg/L 6.6 gpg Moderately hard
- Tulsa, OK 114.5 mg/L 6.7 gpg Moderately hard
- Louisville, KY 115 mg/L 6.7 gpg Moderately hard
- Columbus, OH 120 mg/L 7 gpg Moderately hard
- Cleveland, OH 120 mg/L 7 gpg Moderately hard
- Philadelphia, PA 125 mg/L 7.3 gpg Hard
- Ann Arbor, MI 126 mg/L 7.4 gpg Hard
- Cincinnati, OH 133 mg/L 7.8 gpg Hard
- Chicago, IL 134.5 mg/L 7.9 gpg Hard
- Houston, TX 135.5 mg/L 7.9 gpg Hard
- Milwaukee, WI 137 mg/L 8.01 gpg Hard
- St. Louis, MO 138 mg/L 8.1 gpg Hard
- Grand Rapids, MI 142 mg/L 8.3 gpg Hard
- Fort Worth, TX 145 mg/L 8.5 gpg Hard
- Spokane, WA 159 mg/L 9.3 gpg Hard
- Honolulu, HI 162.5 mg/L 9.5 gpg Hard
- Wichita, KS 170 mg/L 9.9 gpg Hard
- Omaha, NE 170 mg/L 10 gpg Hard
- Los Angeles, CA 192 mg/L 11.2 gpg Very hard
- Lincoln, NE 192 mg/L 11.2 gpg Very hard
- Riverside, CA 197 mg/L 12 gpg Very hard
- Tampa, FL 220 mg/L 12.9 gpg Very hard
- Phoenix, AZ 237 mg/L 13.9 gpg Very hard
- Mesa, AZ 239.4 mg/L 14 gpg Very hard
- Round Rock, TX 258 mg/L 15.1 gpg Very hard
- Pflugerville, TX 267 mg/L 15.6 gpg Very hard
- San Diego, CA 276 mg/L 16 gpg Very hard
- Las Vegas, NV 280 mg/L 16 gpg Very hard
- Chandler, AZ 282.2 mg/L 16.5 gpg Very hard
- San Antonio, TX 299.3 mg/L 17.5 gpg Very hard
- Anaheim, CA 300 mg/L 18 gpg Very hard
- Henderson, NV 304 mg/L 18 gpg Very hard
- Indianapolis, IN 317 mg/L 19 gpg Very hard
- Madison, WI 324.9 mg/L 19 gpg Very hard
- Scottsdale, AZ 352.5 mg/L 20.6 gpg Very hard
- Salt Lake City, UT 353.5 mg/L 20.7 gpg Very hard
mg/L as calcium carbonate. Each classification band is drawn the same width, so the axis is not linear in mg/L.
Systems with similar published hardness
- Honolulu, HI Honolulu Board of Water Supply, 162.5 mg/L (9.5 gpg)
- Wichita, KS City of Wichita Water Utilities, 170 mg/L (9.9 gpg)
- Omaha, NE Metropolitan Utilities District, 170 mg/L (9.9 gpg)
- Fort Worth, TX Fort Worth Water, 145 mg/L (8.5 gpg)
All 60 verified systems How to find hardness in your own utility's report If you are on a well instead