Hardness measures mineral content in water, mainly calcium and magnesium. It's not a health risk but can cause scale buildup in pipes and affect soap effectiveness.

Hardness is measured in grains per gallon (Gr/Gal), with higher numbers indicating harder water. It occurs naturally as water percolates through deposits of limestone and chalk, dissolving minerals. While not harmful to health, hard water can cause scale buildup in pipes and appliances, reducing efficiency. Water below 3.5 Gr/Gal is considered soft, while above 7.0 Gr/Gal is hard. Many households use water softeners to reduce hardness, which work by exchanging calcium and magnesium ions with sodium or potassium.