Water Hardness
Water hardness explained: what causes it, how to test for it, health effects, EPA guidelines, and the most effective treatment options for your home.
Water hardness is caused by dissolved calcium and magnesium. It is not a health risk, but at levels above 120 PPM it causes scale buildup, appliance damage, and increased household costs through higher energy use, more soap and detergent, and shortened appliance life. A salt-based water softener is the standard treatment.
What is Water Hardness?
Water hardness measures the concentration of dissolved calcium and magnesium minerals. These minerals enter water as it passes through limestone, chalk, and dolomite rock formations underground. Hardness is reported in parts per million (PPM) of calcium carbonate equivalent, or in grains per gallon (GPG). One GPG equals 17.1 PPM.
Is Water Hardness Dangerous?
Hard water is not associated with adverse health effects. Calcium and magnesium are essential dietary minerals. The World Health Organization notes that hard water may contribute a small amount of daily calcium and magnesium intake. Some studies suggest a weak protective association between hard water consumption and cardiovascular health, though the evidence is not conclusive.
How to Identify Water Hardness in Your Water
White or yellowish scale deposits on fixtures are the most visible sign. Home test strips ($10 to $15) give results in seconds. Your city's Consumer Confidence Report lists hardness. Professional lab testing provides precise measurements.
How Water Hardness Is Regulated
Hardness is not regulated by the EPA under the Safe Drinking Water Act. It is classified as a secondary contaminant, meaning it affects aesthetics (taste, appearance, household use) rather than health. There is no maximum contaminant level (MCL) for hardness.
How to Remove Water Hardness
- Salt-Based Water Softener Recommended — 97% to 99% removal · Whole house
- Salt-Free Conditioner — Does not remove minerals but reduces scale by 90%+ · Whole house
- Reverse Osmosis — 95%+ removal · Single tap
Water Hardness Levels in US Cities
| City | State | Level | Rating |
|---|---|---|---|
| Yorkville | IL | 380.0 PPM | Very Hard |
| Washington | IL | 380.0 PPM | Very Hard |
| Hutchinson | KS | 380.0 PPM | Very Hard |
| Wooster | OH | 360.0 PPM | Very Hard |
| Bolingbrook | IL | 350.0 PPM | Very Hard |
| Plainfield | IL | 350.0 PPM | Very Hard |
| Howell | MI | 350.0 PPM | Very Hard |
| Medina | OH | 340.0 PPM | Very Hard |
| DeKalb South | IL | 340.0 PPM | Very Hard |
| Garden City | KS | 320.0 PPM | Very Hard |
| Hobbs | NM | 320.0 PPM | Very Hard |
| Orland Park | IL | 320.0 PPM | Very Hard |
| Delaware | OH | 320.0 PPM | Very Hard |
| Lewis Center | OH | 320.0 PPM | Very Hard |
| Dodge City | KS | 315.0 PPM | Very Hard |
| Madison | WI | 312.0 PPM | Very Hard |
| Salina | KS | 310.0 PPM | Very Hard |
| Roswell | NM | 310.0 PPM | Very Hard |
| Dickinson | ND | 310.0 PPM | Very Hard |
| Leesburg | FL | 310.0 PPM | Very Hard |
Top 20 of 658 cities above 60 PPM in our database of 1000 cities. Look up your city.
Frequently Asked Questions
Does boiling remove hardness?
Is hard water safe to drink?
Does a water softener make water safe to drink?
Sources
- WHO Guidelines for Drinking-water Quality, 4th ed. — Health effects
- US Department of Energy Water Heater Studies — Energy cost impact
- USGS Water Hardness Map — Geographic prevalence
Related
Guides: US Hard Water Map
Problems: Hard Water
Other Contaminants: Total Dissolved Solids · Iron
Treatment: Salt-Based Water Softener · Salt-Free Conditioner · Reverse Osmosis