Hard Water: Signs, Costs, and When to Get a Softener

Calcium and magnesium dissolved from rock and soil.

The U.S. Geological Survey defines water hardness as the amount of dissolved calcium and magnesium in water. Groundwater picks the minerals up as it moves through soil and rock, which is why well water and some municipal supplies are harder than others.

Soap is the everyday test.

• Hands feel slimy or filmed after washing, because soap reacts with calcium to form soap scum.
• You need more soap or detergent to get hands, hair, or laundry clean.
• Drinking glasses come out cloudy rather than clear.
• White mineral buildup appears in kettles, coffee makers, and on fixtures.

Heating hard water drops minerals out of solution.

USGS notes that when hard water is heated, as in a home water heater, solid calcium carbonate deposits form. That scale can shorten equipment life, raise the cost of heating water, lower the efficiency of electric water heaters, and clog pipes. If you have both hard water and a water heater that runs out quickly, scale is one of the things to ask a technician about.

Hardness is reported in milligrams per liter or grains per gallon.

One grain per gallon is about 17.1 mg/L, so 7 grains per gallon is about 120 mg/L. The Minnesota Department of Health says hardness can be measured with a test kit or an independent laboratory, and that a community water system can tell you the hardness of its water directly.

It is a choice, with real costs on both sides.

The Minnesota Department of Health says there is no requirement to soften water, and suggests a softener may be worth considering above about 7 grains per gallon or 120 mg/L. Softeners exchange calcium and magnesium for sodium or potassium on resin beads. The benefits it lists are less scale in pipes, fixtures, and water heaters, longer appliance life, and fewer spots and soap films.

It also lists the drawbacks: softened water can corrode pipes, which can raise lead and copper levels in drinking water; the added sodium may matter for some people’s health; the unit needs regular testing and maintenance; and the salt used to regenerate it ends up as chloride in the environment.