What is water hardness?

Hardness is a measure of naturally occurring calcium and magnesium minerals dissolved in water, the higher the mineral content, the harder the water. The following table classifies hardness by category based on mineral content in milligrams per liter. City of Longview groundwater hardness ranges from 69 to 91 milligrams per liter and is considered to be “moderate”. According to the U.S. Geologic Survey, more than 85% of the United States has hard water.

ClassificationHardness (milligrams per liter)


0 to 60


61 to 120


121 to 180

Very Hard

Greater than 180

Show All Answers

1. Why does my tap water appear to be discolored?
2. Why didn't we rebuild the Fisher's Lane water treatment plant?
3. Why didn't we stay with the Cowlitz River?
4. How long will the groundwater supply last?
5. Will the groundwater stain my laundry and household fixtures?
6. Why not move the water supply intake to a better location on the Cowlitz River or Columbia River?
7. What is in the groundwater?
8. Until how long is the groundwater supply expected to last?
9. How do I know the groundwater won’t become contaminated?
10. Where does the groundwater come from?
11. Has there been a change in the pH levels after switching to the new water source?
12. What if the water smells funny?
13. Should I consider getting a water softener?
14. What can I do about hard water?
15. How does hard water impact my life?
16. What is the City doing to reduce hardness?
17. What is the hardness of the City's new groundwater source?
18. Where do hard water minerals come from?
19. Is hard water safe?
20. What is water hardness?