The hardness of water is determined primarily by the amount of calcium and magnesium it contains. Higher levels of these and other minerals make water hard.

Water softening systems work by reducing the concentrations of minerals from the water.

Instead of having higher levels of calcium and magnesium, soft water tends to have higher concentrations of sodium, or salt.

How can you tell if water is hard or soft?
You can’t usually tell by looking at water whether it’s hard or soft. Sometimes the feel of water and what it does to items in your dishwasher or washing machine can be a tip-off.

Just curious