Hardness (calcium & magnesium)
Also reported as: calcium, magnesium
What it is
Hardness is the amount of dissolved calcium and magnesium in water, picked up as water moves through limestone and other rock.
Your body
Hard water is not considered a health risk. Calcium and magnesium are common dietary minerals.
Your home
Hard water leaves scale inside water heaters, dishwashers, coffee makers, and pipes, which can reduce efficiency and shorten equipment life. It also leaves spots on glass, crust on faucets and showerheads, and makes soap lather poorly.
Federal standard: No federal limit
Treatment options that can reduce it
Research & sources (2)
Maryland water systems that reported hardness
- City of FrederickFrederick · 2025 data
- Howard County Department of Public WorksHoward · 2025 data
See common private-well contaminants →
The information on this site is for general education only and is not medical advice. Talk with a qualified health professional about health concerns. Water treatment equipment performance depends on the system, its certification, and proper maintenance.
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